Just fired my RD 350 after rebuild. New seals, bored, new pistons, and rebuilt carbs. The bike started first kick almost. Runs and idles. However it will not pull load without choke on. I was told i could have switched the float bowls. Is this something?
Thanks
well, if it only works w the choke on, then the bowls are correct. yes you can swap them but it will make the choke NOT work.
sounds like you just have a lean condition. probably in the needle if it weill idle w/out choke when its warm. .02
How are the bowls different? The clip is in the middle, 150 main jet and 27.5 pilot jet i believe is what i used in the rebuild kit.
stock pipes and pod uni air filters.
one has the bottom drilled for the feed the choke. the other is blanked.
ok, theres quite a few issues we need to go over though.
1: if you used the needles in the rebuild kit, take them out, they are incorrect. use the stock ones. k&l kit or keyester? wrong profile. the 'yl1' needles they use are patterned after UK 350-b ones and poorly so.
2: you can not run just one size up from mains with uni filters. that's way, way too lean. On a stock rd with unis, your main jet will be in the 190-230 range. I'm not kidding. I know it sounds ridiculous but trust me on this one. run ti for any length of time and you will absolutely hole a piston. remember, the 75s used a ballfed air filter and smaller main, but an unbaffled rd element puts stock jetting at 140 mains. running unis are fine but you have to jet it up. a lot.
3: IF you are not going to run the stock airbox, then see above. IF you have the stock airbox an the bike is stock otherwise, you can get away with 150 mains. mods are going to make a difference as well.
Quote from: m in sc on March 06, 2023, 11:44:33 AM
one has the bottom drilled for the feed the choke. the other is blanked.
ok, theres quite a few issues we need to go over though.
1: if you used the needles in the rebuild kit, take them out, they are incorrect. use the stock ones. k&l kit or keyester? wrong profile. the 'yl1' needles they use are patterned after UK 350-b ones and poorly so.
2: you can not run just one size up from mains with uni filters. that's way, way too lean. On a stock rd with unis, your main jet will be in the 190-230 range. I'm not kidding. I know it sounds ridiculous but trust me on this one. run ti for any length of time and you will absolutely hole a piston. remember, the 75s used a ballfed air filter and smaller main, but an unbaffled rd element puts stock jetting at 140 mains. running unis are fine but you have to jet it up. a lot.
3: IF you are not going to run the stock airbox, then see above. IF you have the stock airbox an the bike is stock otherwise, you can get away with 150 mains. mods are going to make a difference as well.
I used the Yamaha RD350 Carb Repair Kit by K&L from economy cycle. I still have the stock needles i took out of the carbs. It is supposed to be going to Jemco at the end of the month for expansion chambers. How does a 200 main sound? Do the pilot jets also need to be larger? If so any suggestions. I do not have an airbox and not planning on running one. Also deleted the oil injection. Premix.
Thanks,
put the needles from the stock carbs back in, and 200 is a good starting point. also might want to up the pilot to a 27.5 or a 30.
Also right now just running it with stock pipes and unbaffled mufflers. Got a cheap set to start it up because i am putting expansion chambers on it.
I have 27.5 in it now, but will order 30's. If there is an issue with my stock needles. Rocky Mountain ATV has Yamaha OEM needles: Part# 360-14116-04-00. Is this the needle to order?
Thanks
Mikuni Neddle, 5L1 13-5L1 is this the right needle?
i think so. I don't have stock carbs on anything except the r5 and the ds7 anymore. but i know rocky mountain did sell them. before you go through all that, why not to the dave f mod. drill the airjet out to 2.00 mm, get the different jet tubes and 5dp7 needles. common old school mod, will work really well w your setup. john does sell the kit to do this as well. I know, more money, but at the end of the day, this is really worth while. :twocents:
https://www.economycycle.com/shop/yamaha-rd250350400r5ds6ds7-parts/fuel-and-airintake/carburetor-rebuild-kits-parts-related/popular-carb-mod-kit-for-rds/
I think that is what i will do. I will order the dave f mod. What get drilled out the airjet? Do you just need to drill it out bigger with the drill bit included?
yes, theres directions. it the one at the 6 o clock position looking at the bellmouth.
Thanks for info. Will order and update. This forum has a lot of knowledge and has been a great help!
I did the Dave f carb mod. 200 main jet, 27.5 pilot jet, clip 3rd, drilled air jet, air screw 1 turn out, and used old needle with new velocity jet/tube. Hard to start and still only will pull a gear with choke on. Have spark cause I checked it because it was so hard to start. Any ideas? Thanks again
I still don't have the chambers yet. Using stock pipes baffles removed with pod filters.
quote author=m in sc link=topic=5374.msg45542#msg45542 date=1678136421]
i think so. I don't have stock carbs on anything except the r5 and the ds7 anymore. but i know rocky mountain did sell them. before you go through all that, why not to the dave f mod. drill the airjet out to 2.00 mm, get the different jet tubes and 5dp7 needles. common old school mod, will work really well w your setup. john does sell the kit to do this as well. I know, more money, but at the end of the day, this is really worth while. :twocents:
https://www.economycycle.com/shop/yamaha-rd250350400r5ds6ds7-parts/fuel-and-airintake/carburetor-rebuild-kits-parts-related/popular-carb-mod-kit-for-rds/
[/quote]
you need the 5dp7 needle to use that jet tube. (p series)
the 5l1 needle is the stock rd350 one .
Where can I buy that needle? The bike is very hard to start now. :gentleman:
quote author=m in sc link=topic=5374.msg45799#msg45799 date=1679185350]
you need the 5dp7 needle to use that jet tube. (p series)
the 5l1 needle is the stock rd350 one .
[/quote]
I ordered it from treatland! Thanks
The jet needle is not your problem.
Check for air leaks.
cliff
I was incorrect I did use the needles that cam with mod kit from economy cycle.
are you slides in correctly? half moon cutout on bottom towards the airbox
I'll check. I believe so. Thanks
I checked they are in correctly.
quote author=Economy Cycle link=topic=5374.msg45817#msg45817 date=1679253303]
are you slides in correctly? half moon cutout on bottom towards the airbox
[/quote]
Old needle?
I keep re-reading this and the only thing I see that appears off is stock pipes no baffles. That will make it lean and not have any power.
true, but it will run. travis did that with his r5/rd hybrid. it ran but like ass for the most part until i gave him a set of baffles.
whats the ignition situation on this bike?
HPI no battery no lights
NGK NGK Iridium Spark Plug BR8HIX
Cases split and all new seals.
Just thinking what i did to the bike. Yz 85 reeds and reed spacers. Bored .25 over.
Air leak. Check for one.
Compression. What does it have? 120-140 psi should be where a fresh top end should be.
Ignition timing. Check it. See Marks topic on the ignition you have.
Float height. Doubtful, but if you give it too much gas, it'll bog like crazy.
All things good, then unless you need a resistor plug, ditch those for the standard one. If I ran the resistor plug on my bike with resistor caps the bike just ran like shit. Too much resistance was my only other thought.
If your bike is hard to start you need to use a bigger pilot jet, try something like a 32.5 Mikuni and tell me how it starts.
Only use genuine Mikuni jets.
My RD350 has foam pod filters and use a 35 pilot jet. It starts great with choke no problem.
verify spark and that the ign rotor didn't slip. nothing else should be an issue barring an air leak. you did join the 2 cabr sback at the choke crossover?
but a slipped rotor will give hard starting and bad performance overall.
I started the bike again. It started right up and idled with choke on and off. Idle was constant with choke on and off. It did have some unburnt black gas oil mix leaking at one pipe/muffler connector, but i believe that this was from the other day when it did not want to start. I want to blame the starting issue on the inline fuel filters (clear gold stone looking ones). I do not like how they seem to restrict the flow of gas. I am only using them as i just cleaned out the tank. They fill the float bowls but the left carb fuel line does not fill up all the way with gas. I recently rebuilt the petcock and no flow restrictions were present. Carbs are also rebuilt and and float level set to 15mm I think (whatever is spec in manual). I am going to delete the fuel filters as soon as possible.
It still does not want to pull a load without choke. It does seem to be lean on the pilot circuit as someone else suggested. With the way i have been running the bike i have not been able to get it up on the main jet circuit. I am still going to verify timing just to make sure. I should be getting the correct exhaust setup on soon to really verify the jetting. Just wanted to make sure the bike ran and did not blowup into a million pieces before i dropped all the money on the exhaust.
I what to thank everyone for the help/suggestions.
verify spark and that the ign rotor didn't slip. nothing else should be an issue barring an air leak. you did join the 2 cabr sback at the choke crossover?
but a slipped rotor will give hard starting and bad performance overall.
[/quote]
ah. yeah ditch the brass cone filters, they will absolutely starve a motor. i run screened ones or very large brass element onee (canister types).
the other thing that may have been the issue w starting is if the petock seeps when it sits into the carbs, it can fill the crankcases a bit and immediately foul the plugs on startup attempts. *not uncommon
raise the needle to one clip richer, and where are the airscrews? run them in to 1/2 turn in. see if it runs better, if it does, then def go up 1 or 2 on the pilot jet. ideally you want to be at 1-1/4 to 1-3/4 out ont he airscrew to keep circuit velocity where it atomises correctly. But for tuning purposes, ive run them in to as far as 1/4 out then adjusted the pilot size up after.
.02
I was going to put bigger pilot jets in the carbs before i took the bike to get the pipes built. I noticed that both float bowls did not have a hole on the bottom. I had another float bowl with the hole on the bottom for the choke, and I put it on the left side/choke lever carb. Is this correct? I am going to start it today to see if this resolved the choke issue.
Float bowl with hole on bottom belongs on the left/choke lever carb. The float bowl with no hole goes on the right/no choke lever carb.
Correct?
Thanks
^ correct
Also on an RD250/RD350 you can verify after assembly that the bowls are on the correct side. The left (choke) carb should have a brass drain tube nipple that points forward. The right carb drain nipple points down. :twocents:
Also correct as i noticed this after i installed the carbs and reconnected the vent hoses.
Quote from: SoCal250 on March 29, 2023, 12:00:02 PM
Also on an RD250/RD350 you can verify after assembly that the bowls are on the correct side. The left (choke) carb should have a brass drain tube nipple that points forward. The right carb drain nipple points down. :twocents:
I am still trying to figure this out. Got the bike back from Jemco. The expansion chambers look awesome. The bike starts right up and will idle. I moved the clip 1 slot leaner and it appears to have have gotten worse when this was done. What size reed block spacers are members using on their RDs. I have a set on this bike. I was wondering what size 9mm to 13mm thickness? Thanks
6-8mm is fine. that won't cure your problem though. the point behind the reed-spacers, primarily, is to unshroud the boot port. it can move the power band around a bit as well.
try the clip the other way then. always err rich.
I am going to put in the 30 pilot jets that came with the Dave F carb mod, and move the clip back to the middle. I still have the 27.5's in there now. Moving the clip was a test to see how the expansion chambers might have changed it. I am going to try and video what it is doing. Once i get the revs up over where its bogging when trying to start out it seems fine. I am guessing it is still lean. Just hard to believe with the large increase in jet size that I have already done.
you should be able to determine where the pilot jet needs to be by experimenting w the air screw. crank the screw in to about 1/2 turn, if it gets better, go up on the pilot. anything under 1 turn 'good' will tell you this. anything over 2.5 out means you typically need to go down.
IF it idles fine and you crack the throttle and it returns to idle ok w out hanging up, then its probably in the needle. move it 2 clips rich from where you currently are. then try it. theres 5 clip positions, don't be afraid to use any of them if need be. :twocents:
I will give that a try hopefully today. Thanks
Quote from: m in sc on June 14, 2023, 11:45:34 AMyou should be able to determine where the pilot jet needs to be by experimenting w the air screw. crank the screw in to about 1/2 turn, if it gets better, go up on the pilot. anything under 1 turn 'good' will tell you this. anything over 2.5 out means you typically need to go down.
So last night I tried what you said.
The air screw was initially set 1.5 turns out. I went in a .5 turn and it was a bit better. Then went 1 turn in and it was a bit better. Then I went 1.5 turns in and it was better but still bogging when letting the clutch out. Also at this point the air screw was closed off. I also tried turning out on the air screw and from the "stock" 1.5 turns out to 2 turns out which was was way worse as it would stall when letting the clutch out.
I am going to put in the 30 pilot jets that i have and also order 32.5 and 35 pilot jets.
I did some jetting this weekend. Started with 200 mains and 30 pilots, air screw 1.5 turns out, needle clip in middle position. The bike could pull out with minimal bogging. but was still bogging. Once the bike is moving it does not bog. I kept turning the air screw in till closed in 1/2 turn increments and it kept improving. Tried 200 mains and 32.5 pilots, air screw 1/5 turns out. I kept turning air screw in in 1/2 increments till closed and it was still improving, however breaking up in high revs 1st/2nd gear. Ended up going with 210 mains and 35 pilots with air screw 1/5 turns out (need to order more jets). Same as above kept turning air screw in and same situation.
Bike specs: 75 rd350, bored .25 over new pistons/rings, all new cranks seals, yamaha bond (case), and gaskets, new HPI ignition no battery, yz85 reeds, and reed block spacers, banshee crossover tube, uni pod filters, stock vm28 carbs with Dave F carb mod, Jemco expansion chambers.
I am thinking about ordering 37.5 and 40 pilot jets but it seems pretty large. Thanks again.
there you go. i bet a 40 will sort it, its not unheard of at all. :toot:
Thanks for all the help. It seem to be jetted right with 240 main, 40 pilot, clip 2nd position, and air screw 1.5 turns out. Pulls hard on the powerband no hesitation. I think a lot of it was me not being used to a non powervalved two stroke. How ever I have another question. The left carb does not want to fill up the fuel line to the top only about 1/2 way. The petcock has been rebuilt and cleaned. When I was rejecting it 10 times I noticed the fuel inlet nipple was loose. I rtv'ed it but the line still does not want to fill up completely. The right carb does. Thanks again for all the help and knowledge on this forum!
the line may not ever fill up where you can see it full, thats actually normal on a gravity feed fuel system, don't worry about it. glad you got it jetted/sorted.