Hi guys,
I managed to get the RD400c together enough to drive it up and down the street fumigating it.
I have 27.5 pilot (stock 25) 5L1 needle on middle clip and 120 main (115 stock) and 1-1/2 out on air screw. Bike started right up and ran 'ok' in the little jaunts I did in 1st and 2nd. It seemed rich to me so I leaned the needle 1 position. Very nice improvement. Wanted to wheelie even more so and it felt like it wanted to in 2nd. But of idle it didnt feel as good since i leaned it out.
Everything is 100% stock aside from air filter element. I kept the bottom plate with the two venturis and sat a trimmed uni filter on it.
Question is... is it possible my bike wants a 30 pilot even though the stock was 25?
YES. def go up on the pilot
Warm up engine, set idle slightly higher than normal.
Start at 1.5 turns out in the air screw and adjust in and out in small increments until you get the highest idle speed. Give it a moment between adjustments to settle.
When you find the highest idle speed check as setting. less than 1 turn out go bigger in pilot. More than 2.5 turns out go to a smaller pilot
Change pilots if necessary and then set as for best throttle response.
You are jetting, not brewing magic in a cave. You dont need to do it by trial and error
Quote from: rd400canuck on March 26, 2020, 03:52:04 PM
Hi guys,
I managed to get the RD400c together enough to drive it up and down the street fumigating it.
I have 27.5 pilot (stock 25) 5L1 needle on middle clip and 120 main (115 stock) and 1-1/2 out on air screw. Bike started right up and ran 'ok' in the little jaunts I did in 1st and 2nd. It seemed rich to me so I leaned the needle 1 position. Very nice improvement. Wanted to wheelie even more so and it felt like it wanted to in 2nd. But of idle it didnt feel as good since i leaned it out.
Everything is 100% stock aside from air filter element. I kept the bottom plate with the two venturis and sat a trimmed uni filter on it.
Question is... is it possible my bike wants a 30 pilot even though the stock was 25?
How are you going to buy fuel made in 1976? :umm:
Absolutely you will not run stock jetting, unless using canned fuels...not fuel from a pump unless you have a local track nearby that sells race fuel from a pump.
ok thanks again guys...
I never thought about the gas... does the ethanol in it affect affect jetting?
As a follow up to what rodneya posted above, you should download the Jetting Guide from The Tech Library if you don't already have it. It will help lead you through the jetting process so you're not making hit or miss random guesses.
THE TECH LIBRARY »CARBURETOR - FUEL/AIR DELIVERY (http://www.2strokeworld.net/forum/index.php?topic=54.msg170#msg170)
Quote from: rd400canuck on March 27, 2020, 07:57:36 AM
does the ethanol in it affect affect jetting?
yes
Jetting can change a little by temp you ride at and if using stock RD round hole pistons or the Banshee Pro-X pistons I use now.
30-32.5 pilot, 127.5-130 main, 175-P2 needle jet, stock 5L1 needle on #2 pos using stock airbox with Uni filter. 1 1/2 air screw
I disconnect the bowl vent air jet tubes to the air box also.
2.0 mm ignition timing.
Chuck
Check out this site www.rdsonly.com (http://www.rdsonly.com) - now owned by Economy cycles.
click the about todays gas link. great info.
Hope that is helpful.
JT
I'm wondering if it's even worth my time jetting when it's not even 50f outside and ill be riding in 78f on avg.
I have mine jetted so they run in all temps. They run a little on the rich side when it's really hot and humid but they run the best when it's 50-60f. I don't change my jetting with the seasons or extreme temps. I ride when it's in the high 30s as well as in the 90s and humid. I think 50-60 is the perfect temp to jet for.
Quote from: RdsOnly on March 28, 2020, 01:15:03 AM
Check out this site www.rdsonly.com (http://www.rdsonly.com) - now owned by Economy cycles.
click the about todays gas link. great info.
Hope that is helpful.
JT
Thank you so very much for all that info! :cheerleader: :righteous:
Quote from: Jspooner on March 31, 2020, 10:13:41 PM
I have mine jetted so they run in all temps. They run a little on the rich side when it's really hot and humid but they run the best when it's 50-60f. I don't change my jetting with the seasons or extreme temps. I ride when it's in the high 30s as well as in the 90s and humid. I think 50-60 is the perfect temp to jet for.
Plus you have the added benefit of a crisp throttle response when its in the 50's out. Although it gets cold riding home in those temps. I've done it a few times with my summer gear on. Nice when its 75 and sunny, but when the sun goes down it get's my legs shaking lol. Worse when it rains haha.
Quote from: Jspooner on March 31, 2020, 10:13:41 PM
I have mine jetted so they run in all temps. They run a little on the rich side when it's really hot and humid but they run the best when it's 50-60f. I don't change my jetting with the seasons or extreme temps. I ride when it's in the high 30s as well as in the 90s and humid. I think 50-60 is the perfect temp to jet for.
Same.
depends where you live. for me, i try to tun around 70f this seems to be good for the temps i ride in, typically 52-55 to 100.
Thanks for all the input, guys.
I think I'll have to wait till it's warmer regardless. I tried zeroing in on the correct pilot yesterday and the cold got to me. I just want any fun.
Perhaps in a few weeks it'll be warmer and I can take my time and enjoy the process.
I followed the jetting chart from the tech library. Really like that... seems like the easiest to follow.
Seems like, at 50f, my bike wants the stock 25 pilot at half a turn out. When I had the 27.5 in it I turned it to 2 turns out and it revved higher. I'm guessing when it's warmer out I might be able to turn the air screw out a little more.
Maybe I was wrong about the 25 pilot being the right one... I went for a ride today at 1/2 turns out and the needle in the middle. I was doing mostly steady 40-45 mph for 10 mins or so. When I got home I thought the engine felt hot so I pulled a plug and was certainly running lean. Hard to tell exactly because the plugs were dark colored before I set out but they were defo lighter, and not brown in any sense.
I wanted to ask... it seemed to me at that relaxed pace I was barely into the throttle. Maybe 10 - 15% is felt like. Does needle position have much effect at small openings or does the pilot play a big part in riding like this?
I did say to use bigger pilot's... don't worry if you need the air screw out past 2 turns.
Chuck
Quote from: rd400canuck on April 04, 2020, 10:23:41 PM
I wanted to ask... it seemed to me at that relaxed pace I was barely into the throttle. Maybe 10 - 15% is felt like. Does needle position have much effect at small openings or does the pilot play a big part in riding like this?
Pilot
Thanks for that Russ!
Your our home encyclopedia!!
I forgot about that one and didn't have it saved on my computer...
Chuck
Take a piece of light colored duct tape and wrap around the throttle housing. Then pick a spot on the hand grip next to the tape where you can make a noticeable mark. Then use a magic marker and make four marks on the duct tape corresponding to throttle opening: 0 - 1 - 1/2 - 3/4 - F. That way you will know which jet range you are working with.
Lyn Garland
Quote from: rd400canuck on April 03, 2020, 05:15:46 PM
I followed the jetting chart from the tech library. Really like that... seems like the easiest to follow.
Seems like, at 50f, my bike wants the stock 25 pilot at half a turn out. When I had the 27.5 in it I turned it to 2 turns out and it revved higher. I'm guessing when it's warmer out I might be able to turn the air screw out a little more.
2 turns out the pilot was good, why did you go smaller?
Quote from: rodneya on April 05, 2020, 01:12:24 PM
Quote from: rd400canuck on April 03, 2020, 05:15:46 PM
I followed the jetting chart from the tech library. Really like that... seems like the easiest to follow.
Seems like, at 50f, my bike wants the stock 25 pilot at half a turn out. When I had the 27.5 in it I turned it to 2 turns out and it revved higher. I'm guessing when it's warmer out I might be able to turn the air screw out a little more.
2 turns out the pilot was good, why did you go smaller?
When I put a 30 in after the 27.5 seemed to be lean after I leaned the needle the off idle got weaker. I suspected the 27.5 was the right one but I wanted to start over so I went to the stock 25 and put the needle back in middle position. Honestly the off idle to 1/4 really seemed the best with the 25 at 1/2 turns out so I convinced myself it was good until I pulled the plugs after that 10 min ride. TBH the bike ran better than ever before with no dips or peaks in output when I open the throttle.
I didnt realize that the pilot jet played such a major role in 0 to 1/4 throttle. Now that I see that chart that Russ posted I see it plays a very big part in the steady cruising speeds around 45mph. I swear... to keep it at this speed it feels like I am only opening the throttle 15% of the way.
Today I will also mark the throttle positions like suggested so I can see where I truly am while testing
Thanks gain everyone... keep you posted.
I'll put the 27.5 back in and start the process of air jet adjustment testing again to see where it revs the most.
Quote from: rd400canuck on April 05, 2020, 02:13:06 PM
Quote from: rodneya on April 05, 2020, 01:12:24 PM
Quote from: rd400canuck on April 03, 2020, 05:15:46 PM
I followed the jetting chart from the tech library. Really like that... seems like the easiest to follow.
Seems like, at 50f, my bike wants the stock 25 pilot at half a turn out. When I had the 27.5 in it I turned it to 2 turns out and it revved higher. I'm guessing when it's warmer out I might be able to turn the air screw out a little more.
2 turns out the pilot was good, why did you go smaller?
When I put a 30 in after the 27.5 seemed to be lean after I leaned the needle the off idle got weaker. I suspected the 27.5 was the right one but I wanted to start over so I went to the stock 25 and put the needle back in middle position. Honestly the off idle to 1/4 really seemed the best with the 25 at 1/2 turns out so I convinced myself it was good until I pulled the plugs after that 10 min ride. TBH the bike ran better than ever before with no dips or peaks in output when I open the throttle.
I didnt realize that the pilot jet played such a major role in 0 to 1/4 throttle. Now that I see that chart that Russ posted I see it plays a very big part in the steady cruising speeds around 45mph. I swear... to keep it at this speed it feels like I am only opening the throttle 15% of the way.
Today I will also mark the throttle positions like suggested so I can see where I truly am while testing
Thanks gain everyone... keep you posted.
I'll put the 27.5 back in and start the process of air jet adjustment testing again to see where it revs the most.
Don't put too much emphasis with the air screw for this. Do it by how it runs and idles when riding and coming back to idle.
I've run 30 pilots no problem.
C
I actually just noticed it not settling into idle after a mall throttle blip if I went to 1.5 turns out with the 27.5's. I ended up at 1 turn out and went for a ride with throttle positions marked.... for sure just taking it easy and not really going faster than 50mph I rarely pass 1/4 throttle and once i am at a steady speed I am closer to 1/8 than 1/4. OK, so now Ive learned the pilot jet is more than just for idle and immediately off idle like I always thought it was for.
I did notice a little surging when closing the throttle and coasting to a stop from around 40mph. Nothing crazy, ive felt worse but there was still some... does this indicate lean pilot setting or is the normal for completely stock RD400?
Should I am to eradicate the mild surging?
Most stockers have some surging.
What pistons did you use?
C
Orig Yamaha's
That helps a little.
Stock oem RD400 C, D and E models pistons used a burp notch in the bottom of the piston exhaust side skirt to help alleviate low speed surging by burping to the exhaust port at top dead center.
Banshee, Wiseco and Wossner do not use the oem Yamaha notch.
Chuck
(https://photos.imageevent.com/supertune/rddocumentstuff/large/CI-RD400-PISTONS-6.jpg)
(https://photos.imageevent.com/supertune/rddocumentstuff/large/CI-RD400-PISTONS-5.jpg)
(https://photos.imageevent.com/supertune/rddocumentstuff/large/CI-RD400-PISTONS-7.jpg)
Another trick to do when rebuilding the carbs is I drill out the airjet ball then tap for a 5mm x.8 setscrew, to replug, then drill out the air jet and tap for a real Mikuni removable air jet with a 4mm x.7 tap then I use a .7mm air jet over a .5mm stock pressed in jet. this helps run a 30-32.5 pilot jet and helps the surging with a stock baffle mod.
C
ok, I went out farting around town and I went went from 1 to 1/2 turns out and the surging at closed throttle has just about disappeared. Once I get used to the bike like this I'll try the 30 again and see if 1/4 and below throttle improves. Its kind of hard for me to tell sometimes the difference can be so subtle.
I did something really effing stupid today. I was using a 3-cell lipo as a stand in while I was doing all the wiring over the last couple weeks. I totally forgot it was in there and 10 mins into the ride I was sitting at a turning lane waiting to turn and flames started shooting of from under the seat and around the oil tank. I assumed it was fuel and I panicked because there was no way I could put this fire out and I was sure my bike was going to burn to the ground and create one hell of a scene. I pushed the bike to the corner and it dawned on me that it was the battery so I opened the seat and there was a huge fire under it. Black smoke everywhere. I knew there was a chemical fire in the battery bay and if I didnt get it out it was going to burn my bike to the ground. I reach in quickly 2 or 3 times and pull out chunks of flaming lipo. Im so pissed off with myself :( Could have been very bad.
Effed up my finger tips. Doesnt look too bad but hurts like a mofo.
One of the reasons I try to always wear gloves...ouch, but it'll heal :)
God damn! That could've been much worse!
YOW! that suuucks.
:taz:
OUCH!
15 minutes on the wrong charger. Thank God it was on a steel table in my garage. The flames and smoke was unreal.
(https://i.ibb.co/MfXNY0p/batteryburn.jpg) (https://ibb.co/yp3swj5)
My 1976 RD400 C is completely stock with the paper air filter, and a new clean one at that. Please be advised that a paper filter is more restrictive than a foam filter in the stock airbox. This means the bike will need slightly richer jetting with an aftermarket foam filter.
That said, my bike now has 22,000 miles on the stock bores and it has stock jetting. Timing is stock at 2.4MM BTDC. Movable timing mark on stator has been verified and calibrated with a Sanginamiya (Suzuki) dial timing gauge.
Here is the foolproof test for determining if your pilot jet is the correct size: With a warmed up engine, screw in the pilot air screw all the way. If it does not kill the engine, go up 2.5 in pilot jet size until it will kill the engine when screwed in all the way. Always start with the needle clip in the stock position or this test is not valid and if you try to tune the pilot jet with the clip in the wrong position, you will go around in circles and wind up dialing yourself out instead of in.
Now to tune the pilot air screw: Take off in 1st gear and notice if the bike grabs and pulls, or if you have to slip the clutch to keep it from stalling. If it wants to stall and you have to give it gas and slip the clutch, turn in the Pilot Air screw 1/4 turn and try again. Once you are satisfied with the pull away from a dead stop, now go and try decelerating from 3rd or 2nd gear and listen to the pipes for backfires; a few occasional pops is about right, no popping is too rich, and a bunch of burbling and popping is too lean. Another test for this is to simply rev the engine in neutral and see how quickly the tach needle goes back into an idle. If it floats slowly back to idle with backfiring and popping, turn in the Pilot Airscrew 1/4 turn. No backfiring at all and a gassy smell to the exhaust calls for opening the airscrew 1/4 turn.
You should never have to adjust the pilot airscrew more than one full turn either way, from 1.5 turns and if you find you have to, either the pilot is clogged, or the wrong size, or the needle clip is in the wrong position, or your fuel level in the float bowl is off.
RD400 C, D, E have a notch on the bottom of the piston skirt on the exhaust side to "free-port" the crankcase to the exhaust system to smooth out the "bucking" at part throttle. One way to reduce "surging/bucking" when decelerating is to set the idle speed as low as practical, like around 1000 RPM. Also having both slides set so they close equally also helps. If the pilot air screw is a tad lean, turning it in 1/8th of a turn will reduce surging. A good battery and proper timing is also key to getting good idle and reducing surging, they all work together and have interaction, so it's not just the carbs and jetting.
One other tuning note: It is far easier to tune a bike when it is all stock, because if it will not tune with the proper factory settings, there is a problem. Once you have it behaving, in stock trim, THEN go and modify and re-tune. This way you have a baseline because you know the bike will run properly if it is all stock. Without that baseline, you can chase your tail until the cows come home!
Ya thankfully I didnt lose my RD after all the money and effort I've put into over the winter. With the cost of the bike and parts I'm in for minimum $6500. I have to say I thoroughly loved riding the bike before it tried to castrate me with flames. It was everything I hoped a completely stock bike would be. Smooth and reasonably quiet, sounded wonderful.. somewhat torquey down low and not a struggle to get going. Mid range is defo where this bike comes on. Its doesnt have the torque off idle I remember the RD400G having, though but I seem to remember that bike signing off faster up top than this one. Im fairly certain the exhaust ports were lower on the G so that would make sense it it's the case. The throttle pull is a little much, though. That oil pump spring really pulls on it.
Thanks for the advice on pilot tuning, jmendoza. I did notice that stock air filter looked obstructive. It felt almost like a felt to me instead of paper. I have the timing at 1.8. Will I see much off an advantage going to 2.3? I can't remember why I think this but I thought with modern gas it was wise to back off on the advance a little.
Quote from: rd400canuck on April 07, 2020, 07:56:29 AM
Ya thankfully I didnt lose my RD after all the money and effort I've put into over the winter. With the cost of the bike and parts I'm in for minimum $6500. I have to say I thoroughly loved riding the bike before it tried to castrate me with flames. It was everything I hoped a completely stock bike would be. Smooth and reasonably quiet, sounded wonderful.. somewhat torquey down low and not a struggle to get going. Mid range is defo where this bike comes on. Its doesnt have the torque off idle I remember the RD400G having, though but I seem to remember that bike signing off faster up top than this one. Im fairly certain the exhaust ports were lower on the G so that would make sense it it's the case. The throttle pull is a little much, though. That oil pump spring really pulls on it.
Thanks for the advice on pilot tuning, jmendoza. I did notice that stock air filter looked obstructive. It felt almost like a felt to me instead of paper. I have the timing at 1.8. Will I see much off an advantage going to 2.3? I can't remember why I think this but I thought with modern gas it was wise to back off on the advance a little.
I'm unsure in the 400, the info is up here somewhere. But on the 350, stock is 2.0 and we back it off to 1.8 for today's corn fuel.
.5 seems a bit much. But Like I said the info is here. Don't base the 350 timing for your 400, it isn't the same.
Follow the jetting advice Chuck gave you and the procedure that is posted in the Tech Section that was mentioned previously. Do NOT set your timing to 2.3mm!
FYI, the stock timing for a RD400 is 2.3mm, not 2.4mm (as that is for the RD400F Daytona). Less advance should be used for today's fuel if you want your engine to survive. For a 400 you should be using 2.0mm BTDC for today's fuel, and for a 350 you should set to 1.8. Refer to Chuck's advice on this that he posted elsewhere on this site. He knows what he's talking about. :twocents:
Hey guys,
I'm a little concerned with my pilot jetting. Bike is all stock aside from being on the 2nd over bore and I am on middle of stock needle clip. Floats are at 25mm.
The bike seemed to prefer a 27.5 (25 stock) at idle and 1 out but to stop it from surging when slowing down I put it at 1/2 and it really seemed to like that. Out of curiosity I wanted to check how it behaved with 30's in it so put them in put it at 1 turn out and set out for a 1/8th plug chop. Once the bike was warm and ridden for a few I pulled over and put the new plugs in. I did a a steady 1/8 throttle never going over for about a minute. Pulled the plugs and they were bone white :eek:
So I thought maybe the needle is responsible for more than I thought so I put them on pos #4 to richen them a level. Did the exact same thing and the plugs where still white... MAYBE a little less so but they were white. Also, after I put the 30's in the idle was lower and I had to give 1/4 turn on the idle screws to get it back to normal. So... it's defo getting more fuel from the 30's
Am I doing something wrong here? How can a stock bike that came with 25's be so damn lean on 30's?
Did you do a leak down test when you put the motor back together?
Just looking at the top of your plug after a short run is not a plug chop, you need to look at the base of the ceramic part and it only really works for checking your main jet at WOT
With modern unleaded fuels my plugs only start to show color after 15 to 20 minutes or so riding time.
Hi,
I did yes, multiple leakdowns throughout the build. Last one I did was after putting the motor in the bike and the needle didnt budge. I can do it again to make sure nothing changed. Probably a good idea because I noticed the bike seemed to surge more when I would close the throttle with the 30s. It dodnt do it as badly with the 27.5's
well... for fun I went from the 30's to the 35's at 2 turns out. bucked like a bastard at close throttle and low rpm. I went to 1 turn out, was a little better but still surged. I did my usual 1/8 throttle run and pulled the plugs. They are verging on caramel color but still too hot looking.
I'm going to do a leak down again just to rule that out but both plugs behave identically.
I'm just not comfortable doing extended 1/8 throttle with the plus coming out bone white.... and 1/8 is exactly where I am most of the time while steady cruising. The bike really seemed to behave best with the 27.5 at 1/2 turn out but damn! Those white plugs are scaring me.
Could timing cause what I'm seeing? I'm sure I have it at 1.8 ~ 1.9
ok, spent the afternoon checking things over. Did a leakdown test and its still sealed up tight. Held 6 psi for minutes. I got out the dial gauge and check for 1.8 mm btdc and I had the notches lined up perfectly. I got a timing gun but it was only giving out the weakest of reddish light and it was impossible to see the notch on the flywheel through the tiny little window on the stick ign system. So I turned it by hand and each plug caused it to flash on the line or a hair after. So that all checks fine.
Thanks jmendoza for the right up to jet pilot. I put the 27.5's back in and put the air screws to 1/2 out and the bike ran the best it has since I started dicking with larger pilots to try and stop the plugs from coming out white. It sounded perfect idling and revved out nice at 1/2 to 3/4 throttle. It even stopped the aggressive surging that got worse and worse with each increase in pilot. I guess... I'll just stop worrying about 1/8 throttle plug chops. This pilot was what was originally suggested by Supertune I think it was... and that's the one it seems to like best. I just had to prove to myself I guess that it didnt need more fuel and something weird wasnt going on.
Now I will start with needle and main jet chops. 1/2 throttle for needle position, correct?
Quote from: rd400canuck on April 29, 2020, 04:30:03 PM1/2 throttle for needle position, correct?
In theory it's 1/4 to 3/4 throttle.
My experience on street rd400 is start rich and stop raising the needle as soon as you are able to "clear" 1/2 throttle between 4500-5500 rpm on flat road. I'm not saying this is best power, but it worked safely for me.
I tried the plugs thing, but it never worked for me.
You may want to buy a cylinder head temperature gauge, they are cheap and will tell you if something is going sour. Even better if you get one for each cylinder, than you get a better picture.
Hmmm... cylinder head temp gauge.. thats a great idea. It would certainly put my mind at ease. I'm going to start looking for a pair. Would be nice if I could find ones with a settable limit that flashes or something when that temp is reached.
I got these, they were on sale at the time, you may find them cheaper somewhere else:
https://www.treatland.tv/trail-tech-digital-temperature-gauge-in-ORANGE-p/trail-tech-743-et3.htm
Works good so far.
For the price they sure help to let you know how warm up is going and how hot it gets when being frisky.
(https://i.ibb.co/pLnkf8S/SANY2280.jpg) (https://ibb.co/hmCTBjS)
Cylinder head temp is a factor of ambient temp. So you might say you want 350 degrees plus ambient. But in my experience it's hard to run a street bike hard enough to really learn much from cylinder head temp. Also, once cylinder head temp is too hot, the only thing that will get it back in check is turning the motor off. For example, with the Yamaha Kt100 karting engine, you would run it in race conditions but with an adjustable Walbro carb. You might regularly see 500 CHT, but if conditions are bad even 580 could be achieved relatively safely, you could however richen the carb until the needles fall out and that CHT will never fall. There's just too much mass and once it's warm you can't provide enough fuel to overcome that. So for a street bike, something that's run at 20% a lot of the time, maybe 100% for short bursts, what does CHT actually provide? In my opinion, it's a false sense of security and not much else. If it's too lean it's more likely to run cooler actually, as there's less fuel combusting, but since you arn't at full song it's never going to run warm relatively anyways. If it's too rich, it will again run too cool. EGT is likely the best, but trying to do that by watching a gauge I think it s recipe for disaster, especially on the street where attention needs to be directed towards road conditions and drivers.
Thanks for all the tips on CHT displays...
I wasnt planning on using it to tune.... I was just hoping that once tuned, it would be a sign that one of the cylinders is running differently than the other. If I say that happening Id know it was time to take a look for air leaks.
What you guys think?
Here's what my CHTs read on my stage II 400 with B9 spark plugs
start up and go putt putt for 1.5 miles 160
back road cruising 275
hooligan 335
took it to a few track days 310 maybe because it has more air rushing past the cylinders
max I ever saw 340
Noticed there can be up to 15 degree variance between the 2 cylinders and can't figure out why. I think because the sensors are touching the actual spark plug there may be a slight difference in way the plugs shed heat??? Maybe I'll try switching the plugs and see if the symptom follows???
i ordered a pair.... I'll jet by plug colour and set of the pants though. Once Im comfy with jetting I'll just have them to see of one side starts to get hotter than the other as a warning something is up.
Today is needle position and main jet day. Finally got some decent weather here. April was crap.
Quote from: sav0r on May 01, 2020, 11:22:51 AM
Cylinder head temp is a factor of ambient temp. So you might say you want 350 degrees plus ambient. But in my experience it's hard to run a street bike hard enough to really learn much from cylinder head temp. Also, once cylinder head temp is too hot, the only thing that will get it back in check is turning the motor off. For example, with the Yamaha Kt100 karting engine, you would run it in race conditions but with an adjustable Walbro carb. You might regularly see 500 CHT, but if conditions are bad even 580 could be achieved relatively safely, you could however richen the carb until the needles fall out and that CHT will never fall. There's just too much mass and once it's warm you can't provide enough fuel to overcome that. So for a street bike, something that's run at 20% a lot of the time, maybe 100% for short bursts, what does CHT actually provide? In my opinion, it's a false sense of security and not much else. If it's too lean it's more likely to run cooler actually, as there's less fuel combusting, but since you arn't at full song it's never going to run warm relatively anyways. If it's too rich, it will again run too cool. EGT is likely the best, but trying to do that by watching a gauge I think it s recipe for disaster, especially on the street where attention needs to be directed towards road conditions and drivers.
No doubt EGT is a better tool, but CHT is a wonderful and cheap tool to keep an eye on the engine once it is timed and tuned.
I know what temperature my street bikes are running at (considering outside temp and riding style) and if I see x temperature I'll know something may be wrong.
Might not be useful on a race kart, but you find them in airplanes for a reason and I suggest air cooled bikes sit somewhere in between.
I ordered some CHT stuff from amazon. I wanted to avoid brokerage fees and the border. They rob me there.
https://www.amazon.ca/gp/product/B00YY1EFOS/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1 (https://www.amazon.ca/gp/product/B00YY1EFOS/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1)
and
https://www.amazon.ca/gp/product/B00V2A9JN6/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1 (https://www.amazon.ca/gp/product/B00V2A9JN6/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1)
I wanted these so I can power them with 12v and will be visible at night and dont have to worry about a battery dying. Hopefully they work as intended.
So now that I'm ok the 27.5 pilot I decided to mess with the needle height today. If anything... the bike is close I think but my concern is it's lean from the plug colours I see. So I raised the needle to #4 for a little more fuel and went for a ride. It was subtle but the bike definitely felt better in some ways. I 'think' it pulled a little harder while opening the throttle. I did feel that it ran smoother in a way. Like it accelerated smoother and more consistently. Also any surging at various throttle openings and engine speeds has lessened as well. Checked the plugs and they are a nicer caramel brown colour now too.
I'm going to leave it like that... I'm much happier with them on #4. Next is to get some new plugs and do some main jet plug chops. I'm enjoying the bike more and more the more sorted and fine tuned I get it.
Guys... this is going to sound like I'm neurotic but going premix and taking the oil pump spring out of the throttle cable tension has transformed the bike.
Ive been complaining about the amount of effort I have to put into twisting the throttle. Going up through the gears every time I leave a light or exit a corner that throttle made it feel arduous and laboured. Made it feel like I was the one working to get the bike going. So I disconnected the oil pump and added some pre-mix. In the garage alone the ease at which I could twist the throttle was so freaking noticeable. That pump mechanism took a huge amount of force to twist it around... seemingly double of what the two carb springs combined.
Took it for a ride and holy shit what a difference. The bike feels effortless to me now without me having to force that throttle around and hold it in place. The bike has become so much more of a joy to ride it's crazy what a smooth easy throttle did. The bike even feels smooth and less vibraty.. i guess unconsciously I have loosened my grip on the bars maybe. I dunno... the bike feels so effortless to get going and smooth now.
Thats it... I can never go back to oil injection again on this bike. Which sucks because it's so much easier than having to worry about premix and carrying oil on rides... but the bike is a dream to ride more than before. I'm in love with this bike more and more with each change and fine tuning i do. Best thing Ive done was buy this thing and rebuild it to stock spec. Next is the main jet plug chops then I'll be done.
Alright... I finally got around to plug chopping the main jets and I was a little surprised.
I could feel the power delivery change as I opened the throttle past 3/4.. kind of tailed off then picked back up as I rolled it back. I assumed it was because it was rich. The 120's I put in (115's stock) came out bone white. The ceramic was clean clean white and the electrode had white deposit on it as seen in he first pic. BTW I am at 45:1 now.
I put in the biggest ones I have, 130's, and did it again with new plugs and they came out almost as white... maybe... MAYBE a tinge of tan. I must say the bike's power delivery was so much better with the 130's.. no dips or changes... the bike just pulled pulled pulled no matter where I had the throttle while I was on the hwy testing. I'm so pleased with how this bike is at hwy speeds... it's just so eager to go-go-go and wants to rev. I'm losing my fear of taking old two-strokes on steady hwy speeds. If you ask me, this bike could stand some higher gearing... dropping the rpm's by 500 is something I will look into next year.
Ive ordered some 135, 140, 145 and 150's.
Considering I have a 27.5 pilots and needle on 4th.... is anyone surprised I need such bigger jets than the stock 115's? Given the 130 plug chop it really seems I'm going to end up with at least 140's.
No, not surprised... as I told you to go way bigger on main jets for pump fuels today!
Chuck
OK as long as I'm not crazy :umm: :eek: :busey: I also have that uni-filter in there.
It's crazy how sensitive these motors are.. I can see why people end up never getting it right and chasing their tails. I run 4th clip on needle and 1/2 out on air screw. I wanted to try 5th clip and aside from chuffing and steady 1/4 throttle 4000 rpm blues... the bike pulled harder at 1/2 to 3/4. It really seemed, power wise, the bike wants 5th position. Once on the hwy at a steady speed I thought the bike was seizing on me because I could feel the power coming in and out but it was the needle causing it to kind of do this fast stuttering that only went away if I opened the throttle more or the bike was under a load.
Anyway! I went back to 4th position and the well mannered bike returned until I was on the hwy again and noticed some of the same stuttering at steady speeds. I remember I had messed with the air jet... it was at 1/4 out and I usually run it 1/2 so I put it back and the stuttering went away. Learned something new with that one! 1/4 turn on air jet affected hwy speed steady throttle mannerisms.
I'm now wondering if I can keep the 5th clip for the extra power and solve the chuffing and surging with pilot and air screw?
Are the needle jets new?
I always preach...never reuse any of the old brass, only the needle unless bent or the anodizing worn off.
The needle jets are a high wear item...
Chuck
Yup.. replaced eveything in the carbs with all new mikuni stuff. Did anothwr full throttle plug chop with the 130 mains.. bone white.. not even a hint of a ring at base of insulator.
I havent replaced main jets yet but i did just take the bike on its first lengrhy-ish trip. 2 hours at a steady 65-70 mph to visit a friend. Bike ran like a freakin champ. Settles in at 5300 rpm or so.. the vibrations lessen and it isnt that loud at all with the stock exhausts. Bike seems to be pretty thirsty though. 7 liters of fuel to do 100kms. 40 mpg. Is that normal? Its only 11 liters before I have to switch to reserve and I burned 7 of them in 1 hour.
Anywho... i pulled the plugs when i got home. This is after 2 hours of steady hwy speeds. Looks good to me but there is no ring at bottom of insulator.. is that ok?
It's not ok. You have to richen it. Both the main and raise the needle and see how it runs. Are you using a B8 spark plug?
Yes, B8ES.
Damn.. that means needle on 5th and maybe a bigger pilot than the 27.5 - I tried enriching both last week and the bike didnt run as smoothly as it is now, it surged and chuffed just from the needle going from 4th to 5th alone.
What should be my next step to richen up 1/4 throttle hwy cruising? Should I consider the next size up needle jet to let more fuel past at part throttle hwy cruising? If I have to run 5th clip on needle shouldnt I get a fatter needle jet anyways?
I can't believe this thing is gonna get worse fuel mileage than it already does!
40 mpg on modern fuel on these isnt bad at all. shit, my old s2 would get 15-18 mpg when stock. :devil:
Yea I get 35 mpg on my bike if I'm easy on the dinosaur juice. Grab it and go a lot (which is always tempting) and that drips to 25 or so quick.
haha ok... well I wont be taking this thing on any cross country trips then! Certainly thirsty little bastards.
Today I will try the 5th clip position again and play with the airscrew to see if I can get it to behave. I tried it a couple weeks ago just to see and although I felt it pulled harder in part throttle positions I hated the way it surged down low and the chuffing on the hwy at steady speed. I could feel the power shuddering while at a steady 65 mph.
I'm almost tempted to just sort out the fatter mains it needs and call it a day. I hate the idea of undoing how smooth and linear the power is now.. no weirdness, no surging and no chuffing and stuttering at steady throttle... I had it at 70 mph for 2 hours in coolish air and it didnt melt on me so...... I want to think it's safe to leave the pilot and needle as is !!! Here's to hoping.
Ok.. on 5th clip. And turned air screw from 1/2 to 1 out to kill some of the part steady throttle surging. The bike certainly pulls stronger at part throttle positions that's for sure. The plug is a more delicious chocolate brown than they caramel of the 4th clip colour and more of the insulator has it. Still no ring around the bottom but im on the 5th clip and cant go any richer.
I'm going to spend the day dialing in the air screw and see if I can make the bike smooth everywhere like it was before.
One thing I noticed was when I got on the hwy the bike got to 70 mph so effortlessly I didnt even notice until I looked at the speedo. It seems to seriously prefer 5th position on the hwy for sure. Kind of smoothed out more... seems to take less effort to get up to speed. I really like it.
Thoughts on plug colour?
Looking better. What main is in it again? Stock airbox correct?
Yes completely stock intake snorkel and all but I have a lightly oiled uni filter in it.
I am on 130 mains (stocks werre 115's) but I did a couple plug chops and they came out bone white. I have richer jets on order up to 150. Until then I dont pass 1/2 throttle.
id get a cht gauge (the kind that uses the ring under a plug lead) to temporarily use to tune to verify for piece of mind.
From the manual, how the needle and jet react to changes:
(https://i.ibb.co/m0Gcp1R/needle.jpg) (https://ibb.co/Lr8ZKb0)
(https://i.ibb.co/b169cw7/needlejet.jpg) (https://ibb.co/WnHJm8s)
Well... Ive changed my mind yet again, I dont like 5th clip position. Doesnt matter what I do with the air screw something suffers. After looking at some mikuni jetting guides I'm going to wait until I have some reasonable mains in. They show them as having some influence down as low as 1/4 throttle. Maybe I'll get lucky and some richer mains will allow me to keep the needle on 4th where it's almost perfect. I have 1/2 position washers I can try but I'll worry about those after I get the bigger main jets in.
Thanks for those jetting charts... explains the fatter idle and off idle from richening the needle.
I also have some CHT gauges coming :)
I figured since my full throttle plug chops were coming out bone white that I'd go straight from the 130's to the 150's and holy cow lol I got on the hwy near me for a 2km stretch and opened it up and noticed it wasnt quite smooth so I thought "ok, too rich" I looked in the mirror and the entire stretch of hwy, and the cars on it, were completely smothered in smoke... looked like the fog had rolled in on them. I wish I had a picture... when I saw what I had done I started laughing. Everyone must have thought there was a car on fire up ahead but no... was just me.
I guess 140's are next up for a test... Im just surprised 130's were white and just 4 steps up to 150's caused it to be insanely rich. Seems like with such big jumps in fuel delivery it would be hard to fine tune the main.
EDIT - 140's are way better. Bike pulls cleanly no matter what throttle setting or rpm. Only a small bit of smoke is visible after a full throttle blast. Now I'm wondering if I can lean the needle back to middle position, but... worry about that later. Plug chop to come this aft for the 140's
Im starting to think I'm going nuts. Is it possible 140's are too lean and 150's cause it to billow smoke?
EDIT... just backnfrom plug chopping the 145's and they are white. Im so confused... the 150's made it smoke the hwy up and it wasnt able to clwar its throat and now the 145's are coming out white.
Im assuming i did something wromg when i had the 150's in.. but what i dunno. Its just main jets.
I highly doubt a half size will cause that bad of an issue. One half size up from a good jet might make you foul a plug or two but it's safe. It won't cause an issue usually.
I'd take a step back and a deep breath. Make sure you're cutting the throttle at a good WOT run and cut the threads off to be sure you are seeing the base of the porcelain correctly.
It sucks but unless you stick to a fat main and a burbly inefficient top end you have to be able to see the porcelain correctly. A handful of 3 dollar plugs is a lot cheaper than a mistake in jetting.
Quote: I looked in the mirror and the entire stretch of hwy, and the cars on it, were completely smothered in smoke... looked like the fog had rolled in on them. I wish I had a picture... when I saw what I had done I started laughing. Everyone must have thought there was a car on fire up ahead but no... was just me.
The carb jet wasn't causing that. Something else must be going on. There must of been oil pooled in the crankcase or something with it getting too much oil. Did the smoke clear or keep coming?
nope... it was just rich as hell with the 150's.... i could tell on my way to the hwy that it was smoking more than normal when i would goose the throttle a little on the way to the on ramp and on the hwy it didnt clear up at all as I went tearing up it.
What I am doing is warming the bike up and riding about 5 to 10 mins before pulling over... putting the new plug in right near the hwy on ramp. Then I start it up and go up through the gears and hold it wide open in 6th as long as I can. It usually makes it to 8000 rpm before I hit the kill switch, chop the throttle and pull in the clutch to pull over and have a look at the plug.
Is that long enough at wot to get the plug insulator hot enough to show a ring or coloration at all? I think im getting to about .7 of a mile before having to chop it. The bike is going way too fast at that point and I am sort of forced to let off.
Something is going on... I aint doing something right. Today I will put the 150's back in just to make sure I'm not nuts and it is indeed rich as hell.
ok, 150's back in... checked everything over and went for a ride and hit the hwy... I dont know what the eff I did the other day but the 150's aint smoking now like they did. no clue... maybe the float was stuck and the bowl was over filling and i didnt notice it. I have no clue but now its running fine. Beats me!
So.. i need more new plugs but if I had to guess the 150's are too lean. I'll order some 155's up to 170's. The bike pulls smoothly with them as I twist the throttle to wide open and back at different rpms... I cant really detect any dips in power delivery like I could when the jets were 120 and 130 so it seems this bike really wants a lot more fuel. Im going by the fact that it doesnt seem to pull into a wheelie when i am fuel throttle like it would if I hold it at 3/4 or a bit less. Also, no I'm certain the needle needs to lean out to the stock middle position. The fatter mains are richening up the needle a lot.
I know I keep saying this but... is anyone surprised a stock bike will go from 115's to possible 170's or so?
150's mains are way too rich for your stock setup... 130-135 I would think is would be max.
Chuck
I'm completely confused then.. plug chops were coning out bone white with the 130's and even the 140's. But another weird thing... I was able to get to nearly 100 mph with the 150's. Would it be able to do that if it were really rich?
I'm getting new plugs today... am gonna plug chop the 150's just to see. I'll wait till this evening though... it's hot and humid here like crazy.
How long are you on the throttle when doing a plug chop? It's supposed to be between 20-30 seconds... if I remember correct?
I try to short shift a bit, still hairy though.
I hold it for 20 seconds at the most I think. After a good warm up I put in new plug... I short shift right into 6th asap then hold it wide open till it pretty much almost stops pulling and im near 100mph. Hit the kill switch, close the throttle and pull in the clutch and brake to a stop. If it needs to be longer than that I'll have to come to a near stop then repeat it... I'm just going too fast and the bike is screaming near 8000 rpm. This bike could definitely use a tooth on the front sprocket if you ask me.
I have 8 new plugs... gonna plug chop the 150's this aft and see what comes out.
Plug chopped both sides with the 150's. No rings at bottom of insulators and electrodes are white. The first two pics are the right side.
I guess.... just keep going up sizes and see what happens or could there be something else causing this?
I don't know if this is good advice or not but I jet my bikes for the type of riding I do most, which is back and forth to work and the occasional rip thru the gears on a back road and I run the same jetting all the time, I don't change it based on weather or temp or whatever. I don't worry about if it's going to last at WFO in 6th gear for XX minutes or seconds or whatever because that's NOT normal riding. Unless you plan on using it to outrun the cops everyday or its going to be a track bike or something like that just get it so it runs good where you are comfortable riding it 90% of the time. My trip to work includes about 5 miles of freeway and I usually will ride about 80mph or so on that stretch maybe occasionally taking it up to 100 or so where I know it's safe to. I haven't had a problem yet. Don't get me wrong, I do go out and do a plug check after doing a top ender but I don't place all of my time and effort on that..................I would if I was jetting a race bike tho.
Hey JSspooner... is true.. I could get by with the seemingly way too lean 130's I had in it for the longest time since I rarely went past 1/2 throttle and even more rarely past 3/4.. spend most of my time at 1/4 or less where the bike runs like a champ. But... I want all the power this thing has to offer even if I dont use it all the time. If i open it to 100% then I want it to make 100% power that it can make. Right now its way too lean and dangerous :eek:
Are you sure everything else is correct, timing, no air leaks, etc.? Like Chuck said, 150 should be way too rich on a stock bike.
Me too about the timing. Are you sure that isn't advanced too much? Here's a pic of the ring.
(https://i.ibb.co/HtWFJZt/plugchop.jpg) (https://imgbb.com/)
are you sure the uni filter is sealing all the way around? :umm:
Just an idea...What % of ethanol is in your gas? If it is way up there it may explain the big jetting.
I'm not sure what to do... I was looking into how timing affects an engine and no where I can find anything that says too little or too much advance will cause what I'm seeing. I rechecked the timing a month ago and if I remember I was 1.8 btd. I dont have a timing light though... I was using a light bulb and seeing when the bulb would turn on as I rotated the crank and both sides were when the pointer was at the mark that I set with the dial indicator at 1.8 mm.
The gs pump says "up to 10% ethanol" and I am using regular not the expensive high octane stuff. I'm assuming this isnt a high compression engine and doesnt need that much octane.
I'll go check the air filter but as far as restrictions go... it still has to suck air through that rubber snorkel with nostril sized holes in it. Would a free flowing air filter or one that isnt sealing properly cause what I'm seeing?
Thanks guy.. I'm confused! And it's definitely getting more fuel... the needle is now too fat and feels like i need to put it on the middle form the fourth.
the filter matters for sure.
10% is normal, or advertised as 10%, thats not it, that -may- warrant 1 jet size, maybe. set timing to 2.0 or 2.1 on a 400. :twocents:
Ok... i cut the plugs to make sure I wasnt missing and sure enough there are rings. In shade it looks grey and in sun its caramel-ish. That chop was with the 150's in very hot humid weather today and they are perfectly even both sides.
Included is pics of the airbox set up. Its uni filter but i run the bottom of the stock filter for the two venturis. It sticks up about half in and is compressed when lid is on. Its also oiled a little. I had already doubled checked the leakdown test a month ago or so and again, it was perfect so I doubt there is an issue there.
Now the needle is rich though... so I'm going to put it on #3 from #4 and see how it behaves... If I like it I'll do another plug chop. Then ill time it at 2.0mm and chop again and see what's up. Judging by the plug chops today I think I am still too lean.
If your bike works good with the 150 main, I would leave it.
Ya.. everything points to it needing bigger mains than anyone expects including me so I'm just gonna run them. The entire throttle range is seamless now.
I just leaned the needle a position back to #3 and did a 1/2 plug chop. The bike ran better.. position #4 got too rich with the bigger main jets. This bike does NOT like to have too much fuel at steady throttle hwy seeds... it chuffs and does like a mild quick surging. Here is the 1/2 chop pics. One with flash and one without.
The 100% chop has been leaned out by dropping the needle a position. I will put 160's in it when i get them... then i think ill be done... i hope.
thats crazy.
however, as is always said: the bike will tell you what it needs. If it works it works. :cheerleader: :patriot:
Ya i dont get l :umm:
I have 175-P2's in there.. I think that's correct. I starting wondering if i had the wrong needle jets in there causing it to lean out.
I'm excited to get jetting sorted so I can finally install my HPI electronic ignition and feel the difference. I'm super curious about that.. I'm almost afraid to, though! The bike is a joy to drive as is... I hope it only gets better. I might wait and bring it with me in Aug to Deals Gapp if you guys are welcoming canucksters across the border then. Also, I wouldnt mind a smaller rear sprocket to be honest. I have the econocycle conversion on it... i feel the bike could benefit from a few missing teeth. Like... maybe drop the revs by 500 rpm in 6th.
Well, the last thing you have to worry about is a soot fouling problem. :vroom:
lol ya... I wont be fouling any plugs :metal:
I just picked up 160's and 170's. I have plug chops prolly tomorrow if its nice out.
Edit.... 170s are way rich. It wouldnt pull past 6500 rpm and burbled. I'm starting to think the 150's are very very close. Ive leaning the needle to #3 the 150's came back a little lean looking on the ceramic so I think 155's might be the ticket. Anywho... I have 160's and want to know what they look like so thy are going in for a plug chop.
This chop is 160 main. Im a little surprised the 170s were the entire insulator and the 160s seem to be a 2mm ring however, it was scorching hot and humid for the 170 chop and today its kinda cool.. It actually felt a little rich I think. It pulls cleanly until it get to 7000rpm then I think I felt it trying to go higher but i felt the smallest sensation of burbling. I also think the needle is the tiniest bit rich.
So... i dunno. I think the 150's might be the ticket. I'm never going to be full throttle for more than a few couple seconds anyways.
Question... is there a noticeable difference in something like a 150 to 155 ? I'm under the impression a jet with a 5 at the end is a half jump and only for really really fine tuning.
Alright, I m done with plug chops and jetting. When a 170 drowns the motor and ceramic and a 160 gets me a ring (but still burbles a little at 7000 rpm) I'm beginning to wonder just how accurate plug chops are in this motor. The discrepancy between the 170 and 160 doesnt make any sense to me. It could be me doing something incorrect but I do the plug chops the exact same way every time.
That being being said I am going with 150's, needle on #3 position and a 27.5 pilot at 1/4 out (slows idle but this prevents it from bucking on decel).
With these settings my bike pulls cleanly, steady state cruising is smooth (no chuffing) and the pull is linear and proportional from off idle to wide open. I'll keep my eye on piston tops (right now they are almost clean from being lean) and will add my CHT displays when they arrive but for now jetting is done in my books.
Thanks for all the help everyone. :clap: :clap: :clap:
Me again :metal:
Im so dumb i should have done this from the start.... i went out and bought a timing light... the timing was so retarded it wasnt even funny. Perhaps an entiee millimeter. I set it to 2.2mm and went for a ride and major difference. Befoee the bike wouldnt rev past 7200 in firat or second gear rpm now it will spin past 8500. Setting the timing with a little bulb isnt accurate afaic once the engine is running.
Once the rain lets up im going to do plug chop again and hopefully the results dont confuse the hell out of me anymore.
that would explain it. :bacon:
Quote from: rd400canuck on June 02, 2020, 05:08:33 PM
Me again :metal:
Im so dumb i should have done this from the start.... i went out and bought a timing light... the timing was so retarded it wasnt even funny. Perhaps an entiee millimeter. I set it to 2.2mm and went for a ride and major difference. Befoee the bike wouldnt rev past 7200 in firat or second gear rpm now it will spin past 8500. Setting the timing with a little bulb isnt accurate afaic once the engine is running.
Once the rain lets up im going to do plug chop again and hopefully the results dont confuse the hell out of me anymore.
I'm confused, timing is timing no matter what method you use to measure it. :umm: Would you mind telling me how you timed your engine using the timing light?
Hi Alain,
The first time I did it I used a little bulb that would come on when the points closed as I rotated the crank with a wrench. I set the adjustable pointer to point to the notch at 1.8mm then adjusted points until the bulb would turn on when the pointer and notch were aligned.
things is... after I do that.... then start the motor and use the timing gun to check.... the notch is showing up after the pointer by a decent amount.
this is exactly why you use a dynamic timing light. glad you found it :cheerleader:
Quote from: rd400canuck on June 03, 2020, 08:18:23 AM
Hi Alain,
The first time I did it I used a little bulb that would come on when the points closed as I rotated the crank with a wrench. I set the adjustable pointer to point to the notch at 1.8mm then adjusted points until the bulb would turn on when the pointer and notch were aligned.
things is... after I do that.... then start the motor and use the timing gun to check.... the notch is showing up after the pointer by a decent amount.
I understand the process you used (which could explain the error), but I think you meant to say when the bulb would turn
off (when the point opens).
Now put that bad boy at 2.0mm and enjoy! :celebrate:
wrong post. igore
Two things that I can think of.
When you change direction on the crank there is a bit play that you will need to take up by going past your ending firing point then going regular direction to set your ignition. Watch Mark's awesome vid https://m.youtube.com/watch?v=Iqardto3Kbs&t=186s
Also I think that the HPI is advancing a bit at idle so maybe you need to up a bit on your jets.
.. except hes running points. :vroom:
switching to HPI now.. in another thread though
:patriot: