I have a couple of spare engines and would like to build or have one built for street duty with more mid range. Meaning keeping the top power range near the stock range. Of course more up there there would be perfectly acceptable, too.
Is there a recommended recipe for getting that? Like who to do the porting if it calls for that? Who to do the head mods if it comes to that? Recommended size carbs if bigger than stock would be able to help the mid range.
Again, this would be a street bike not a racer. It would just be nice to have even more mid range power and torque, if possible and practical. I already have a set of Bassani chambers to go with the combo.
I appreciate the consideration and information on this. :like: Thank you!
Give me a call 702-858-9177 Check out my web site richstaylordporting.com WE can have a counselng session
Rich
I'll do just that. Is a particular time or day better?
Prety much available most any time. Im in Utah MT time
Rich
RD350 engines? There's loads of power you can squeeze out without raising the RPM ceiling - that's what I wanted for mine. Porting, heads and custom pipes can do low / mid 50s HP, with power from 5.5 through to 8.5k. I think just the right pipes alone would be a big boost.
You could do a pipe to bring things even lower than that but there's already quite a lot of exhaust timing / blowdown on a stock 350 so that would limit things a bit.
COOL! That's just what I am looking for.
Any tips you could pass along would be much appreciated.
Don't forget that a programmable ignition can add to the low end AND the high end.
I'm just a hobbiest, but this is what I did, I'm sure others might do it similarly - you could probably go 1mm higher and not as wide on the exhaust and get similar and perhaps better ring life. I've not tried back to back.
I raised the exh port to 28mm and widened it to 43.5/44. Raised the transfers to a 42mm and milled out the roof of the little one as much as I dared to open it up and match the roof angle of the A transfer better. I also redirected them as best as I could to get the streams closer to Jan Thiels model. Cut back the base of the main transfer by about 8mm, and also got rid of the hump in the tunnel. Raised and opened up the boost port to 18mm and pointed it just in front of the spark plug. I skimmed the barrels for 400 gaskets and pinned the heads on centre. I recut 250 heads to give 45% squish by area and 0.85mm clearance - total head volume is about 24cc.
Running aftermarket chinese cylinders, prox banshee pistons, standard reed blocks with YZ85 reeds, banshee inlet rubbers with link pipe and stock 28mm carbs with the Dale F mod. Single large foam filter on the standard intake rubber. HPI ignition.
Made pipes to a design by Mick Abbey in the UK - It was quite close to what I came up with on the 2t exhaust calc sim, but with a few notable differences. The overall length was almost identical. You want pipes for an 8.5k peak or thereabouts. Speak to Mick or someone local here in the US and tell them what you want the pipes to do.
I've not dynoed mine but it's smooth all the way through to 9k and will pick up the front, smartly, in second from about 6k. It's a really nice engine.
Is there a thread you can reference on the ignition and the curve that you recommend?
I am taking notes on the porting and head work. You are far more skilled than I in those areas, but they give me information.
Thank you.
broad squish is a good practice for low to mid range, ive seen a few triple guys do it. most pipes quit making power at 9k anyway, unless oyu get real juicy wit them. with bassanis, you'll be fine. as far as a midrange ign curve, you can basically go 17 degree at idle, then right to 22 degrees at 2k, 24 at 5k, then 19 at 6.5k, 17 at 8k. 15 at 10k, and then 7 at 10.5k. (if you go programmable) this will sign if off nicely early. thats a rough idea, but you get the point.
I got the bog stock HPI system which only has one curve - you can check it out here:
https://www.hpi.be/item.php?item=210K176
Seems to work alright but people do make decent gains dialing in a custom curve. I love the little flywheel.
I want to try making a 4mm stroker next time I build one. You pick up a load of time area from the longer stroke, which is tough to do with the limitations of the castings at 54mm. On a 65mm Bore, you'd have an RD385 and probably a genuine 60+hp somewhere between 8-9k, without crazy porting. Pretty sure it's possible with some fiddling around.... :guinness:
What programmable ignition are you referring to?
I am very familiar with quench if that is the same as what you call squish. I have used it for many years on my big block Mopars.
Please keep the info coming, I am learning a lot.
Thank you.
zeeltronic with a vape cdi is what i run. there are others but this is my preference.
its sort of related to quench, some people interchange the terms but the effects in a 2 stroke can be VERY different than in a 4 stoke. (Particularly in an RB engine.)
squish will direct the mixture to the center and keep it cooler at the piston crown edges. the wider it is, typically the more midrange you can get. I know a guy with an H2 thar builds power, and a lot of it, off idle to like 7k, but hes at like 50-60? percent squish area (might be more), its ridiculous. however, his head volume was almost stock after recutting. so, squish doesn't nec affect compression as long as the volume is addressed. but it can direct the mixture where you want it to land in the chamber, which can affect (greatly) how much gets out of the exhaust port on compression stroke, for one thing, and how the transfers can be shaped.
I get what you are saying. It would seem that it would take a good bit of trial and error to nail that down.
I also see 250 heads mentioned often. Is that only due to the smaller combustion chamber or is there more to it than that? And are they better to start with to modify or are the 350 heads about as good?
There's been a lot of research done on squish velocity, apparently the numbers to shoot for are something like 20-29m/s at peak power RPM. If peak power RPM is lower, you need a greater squish area to achieve it (squish angle also is a factor.)
Fortunately for us plebs, clever people have been experimenting with RD350s for decades, so anything 45-50% is going to work well. I'm pretty sure I set my compound angle to 14 degrees (will check notes later), which should be fine for RD/YPVS pistons.
250 heads are good because they're way cheaper and more plentiful than 350 heads and you have a little more metal to play with. The only prob with all US 250 and 350 heads is that they're all for the short plugs, so to get the sort of chamber volume you need for pump gas, you might have to put spacers under the plugs to pull them up a tiny bit once you're done.
This is how I do them. Pick out a pair of vaguely matching heads and lap the faces on a surface plate, just to clean them up. Then measure from the top of the plug. Put them in the mill and clean up the top of the plughole and head bolts until they are equal.
Make an arbor to hold the heads from the plug hole, which is just a piece of mild steel, machined down to 1" diameter with a 14 x 1.25mm thread on the end and a centre reference. You can use 5c collets on my lathe, which hold everything accurately and are handy for this.
Once it is all mounted up, spin them up and clean up the gasket land, about 15 thou on each. After that, you can measure the height from the centre reference and work out the hyp, to scribe an accurate OD on the head for where to start cutting the squish.
After that, set the squish angle on the compound and cut until you hit the OD. It doesn't matter how wide it is at this point as you need to recut the bowl anyway.
For the next bit a radius turning tool is helpful. I worked out that a 28mm radius would be a good starting point for a bowl that would intersect the squish band about the right point (you can mark up the id of the squish on the part with a pen, same as before. This gives a single radius bowl of a little over 12cc total vol, which added to the vol under squish (about 5.5cc) and the tiny bit in the plug recess makes for a hair under 18cc. This might might work on 100LL, which could be fruit for a future experiment as it's a doddle to cut.
For pump gas you need more vol (how much exactly is a bit of an open question, depending on your gas / altitude / tuning etc) but I'd say min 22cc, which is about what the stock 350 heads have. I cut this a bit at a time with a large radius tool bit, using dyechem to mark up the bowl, a bit like wood turning. You need to stop and measure with a burette regularly, but you get a feel for the cuts and the vol and it doesn't take long.
Here's a couple of pics of the tools / process.
(https://i.postimg.cc/rzSrwZyR/6-E0-D98-CA-DAF6-486-F-8-D63-8-A85099-D311-B.jpg) (https://postimg.cc/rzSrwZyR)
(https://i.postimg.cc/WhTJFmtW/FA013546-5-DB5-4-D8-A-BF47-799612534-E82.jpg) (https://postimg.cc/WhTJFmtW)
another way around it is to oring the heads, this moves the whole casting down which will basically require you to recut anyway. (using the short reach plug heads, us models 70-75). however, VP makes a nice billet head if you're willing to spend a bit. I'll be going that way on my t500 as the stock heads are just fucking garbage.
https://vintageperformanceproducts.com/shop/ols/products/yamaha-rd350-billet-heads
Those billet heads are really nice. I'm going to find a pair of late model Euro 250 1A0 heads next time - they have an extra fin and are for long plugs, so you have a lot more to play with. In a, probably rash, move - I decided to bite the bullet and ordered the cheapest, taiwan made, 4mm banshee crank I could find yesterday. Will let you know how I get on with squeezing it in...
Quote from: m in sc on October 16, 2024, 11:42:02 AManother way around it is to oring the heads, this moves the whole casting down which will basically require you to recut anyway. (using the short reach plug heads, us models 70-75). however, VP makes a nice billet head if you're willing to spend a bit. I'll be going that way on my t500 as the stock heads are just fucking garbage.
https://vintageperformanceproducts.com/shop/ols/products/yamaha-rd350-billet-heads
Their dyno sheet shows about a 10% improvement in horsepower AND torque at 8,500 or so. From just a combustion chamber change. Seems a bit optimistic to me. Does it to anyone else?
And I would prefer to stay with the OE look. But that is not set in stone. Can that combustion chamber be accomplished with the OE head? And at what cost? I always run 93 octane anyway as a safety factor. O-ring is usually a good thing and I used to index plugs on our wedge engines so spacing the plug up is no big deal.
:like:
no, it makes a notable difference of done well. you can get a lot done with stock heads... finding someone to profile them though, thats another story. i have had had a few sets (modded stock ones) that either i did or were done , its not that bad. if you are competent on a lathe, its not -that- hard. just reangling the squish and correcting the height and chamber volumes is pretty easy
So, who here is competent with this procedure on OE heads and wants to do it? I have spare 350 heads now. But if enough better, I would find a pair of 250 heads.
I just looked into the Zeeltronic and Vape. :eek: I was shocked. One is on sale and the other is on back order. But together they are about $845. I have bought a lot of ignitions for my cars over the years but have never paid anywhere near that much for one. Or even two. Just WOW!
Quote from: RDDave on October 17, 2024, 09:13:28 AMSo, who here is competent with this procedure on OE heads and wants to do it? I have spare 350 heads now. But if enough better, I would find a pair of 250 heads.
I will be experimenting with them over the next year. Just bought my license for engmod and need to get it all set up for the RD now.
"license for engmod" ?
What is that?
engmod is a very sophisticated engine modelling software - you can model everything from intake through to exhaust as a system.
I'd think about the whole package before you get cutting. 350 barrels need the lip skimmed from the top, for o-ringed OEM heads, or RD400 gaskets and you kinda need to do that before you can set the squish gap. Also, total head cc is going to be dependent on the rest of the tune (porting and pipes.) A stock 350 has a head volume of about 22cc and runs fine on pump gas. Add good porting and pipes and it probably won't, as the dynamic compression goes up from the effects of the tuned pipe. Mine had detonation @ 22cc / 0.95mm squish gap. Still at 23cc / 0.95 and eventually cleared up at 23.5cc and 0.85mm. An experienced tuner will have done all the experimenting already.
I like the HPI ignition which is relatively cheap but seems to work well. Doesn't have a lot of output for lights but works fine with LED bulbs.
yup the vape is pricy but worth it. i run 4 currently... they are that good. ;)
is it nec? no. absolutely not. the hpis is great, as is just a dyna-s.
But its also the charging system.
so by comparison... figure a full msd billet distributor, a 6al, super nasty coil and a 150amp alternator equivalent with a tunable curve box. (car). thats what you get. OR... similar to this.. https://www.jegs.com/i/MSD-Ignition/121/7531K/10002/-1
I don't mean any disrespect but that system is for a complete ignition system and will do just about everything that you might EVER need an ignition system to handle. I count 3 main components, 3 wiring harnesses, O2 sensor and harness, 8mm wires, etc. Very, very few hot rodders would ever need that one. You notice that it has NO reviews. And that is for a system for SBC which is probably the most common application on the planet.
Hardly the same as a simple programmable CDI. Not really an apples to apples comparison.
Since I am not a hard core racer, bang for the buck, or ponies per dollar comes into play. The head mods interest me greatly, but I simply cannot justify that much money for just an ignition.
But I don't want this conversation to get derailed. I am learning so very much and I appreciate the willingness to share so much hard earned knowledge.
Thank you.
One thing that does surprise me though is that I cannot find any dyno tests on mods to our bikes from anyone other than a vendor. Am I looking in the wrong places?
you aren't wrong... but, well i cited 2 scenarios. the 1st being comparable. the 2nd being off the rails. (as far as car stuff), so i agree, it's not comparable per say. For what you get benefit wise from a cdi for these bikes... its worth it. adding a dyna, for example, then trying to chase down charging issues is a common occurrence. the vape cures all that. the zeel is an add on from a different supplier and not 100 nec. on my t500 and 70 r5, they run a straight timing curve. 2 rds run them w boxes, and my tzr has a programmable cdi.
vape is 500 bucks with charging system included. an hpi is around 300 but has a mush weaker charging, but bang for buck, its the best hands down as its a complete system. A dyna for an rd is over 300 to run on stock coils and stock charging. its the easiest to install though.
dyno runs are usually not very easy to find. one change doesn't usually do a whole lot, and its easy to get big numbers, but at the cost of rideability.
Have a peek on Mick Abbey's Facebook page. He's a UK tuner that does a lot of vintage stuff and almost always posts dynos of his results. He's an absolute gentleman and has given me a lot of really useful tips. This is for a 350, and was what I was aiming for with mine...
https://www.facebook.com/photo/?fbid=2703540803238979&set=pcb.2703540876572305
I see the trade-off.
30% loss of power below 4,000 is a lot. But man, that thing rocks 5k on. I would like to ride one just to see what the area under 5k was like for street driving. Losing a full third may make it a pain. Like a big lumpy camshaft, what is fun for one is intolerable to another. I wonder what the happy medium is? Less bottom end loss vs how much more power in band?
I sure would like to ride one on the street to see what it's manners are and to see more dyno sheets. But......
Thank you for that, it is very informative.
its hard to know till you do. I'll be honest, they are fine. if you want midrange.. these really aren't the ideal bikes for that. the closer to stock the better for that, including pipes..... piston port models are great mid range. BUT, you -can- get decent midrange out of a stock ported/stock head setup.
heres my 72 R5 with an rd motor in it. ebay cyls, FP (vintage) chambers, cdi and programmable box with cheap flat-slide with a y boot & k&n & some v force reeds. its quite useable from 3k-on, and this is primarily due to the ign curve and not going too big on carbs. not sure about HP numbers, really dont care, but it gets to 100 quick and has good manners around town
watch the tach.
Totally agree, with m in sc. Without powervalves, best you'll get is about 3k rpm of usable power and some overrev. Where you want it, depends on the ports and pipes. It's difficult to shift the hit much below 5.5k though, because the stock port timing is already pretty racy.
FWIW, I suspect that dyno is not a like for like comparison under 4k, good chance he's only opened the taps at 4.5k or so. Mine is nice and tractable from about 4k, but it's not going anywhere fast until just under 6.
I grew up roadracing 125s so 6-9k IS midrange for me! :haw:
That R5 sounds sweet!
Quote from: m in sc on October 18, 2024, 05:14:46 PMits hard to know till you do. I'll be honest, they are fine. if you want midrange.. these really aren't the ideal bikes for that. the closer to stock the better for that, including pipes..... piston port models are great mid range. BUT, you -can- get decent midrange out of a stock ported/stock head setup.
heres my 72 R5 with an rd motor in it. ebay cyls, FP (vintage) chambers, cdi and programmable box with cheap flat-slide with a y boot & k&n & some v force reeds. its quite useable from 3k-on, and this is primarily due to the ign curve and not going too big on carbs. not sure about HP numbers, really dont care, but it gets to 100 quick and has good manners around town
watch the tach.
the point of me posting that was to show even w stock porting and heads, they -can- be quite useable down low while retaining good high rpm power. IMHO thats about as good as it gets w out cutting heads. I have heard of quite a few people actually going down to 26mm carbs, which isnt a bad idea (as counterintuitive as that may be). but keep in mind, the LC/RZ and Banshee came stock with 26mm carbs.
Your bike pulls clean and pulls hard. I would be very happy with that combo. I have cleaned up the Bassanis and am repacking them now. Should have them on today and do a test ride.
I am fairly committed to the head mods. And am considering new carbs since they are not a ton of money and you have provided enough information to get it real close to start.
My bike starts and runs good, but compression is down at 95lbs. I plan to pull it down this winter and see if rings will do it or if it needs more. It doesn't rattle and with only 5,000 miles, a simple re-ring is possible.
The recipes and tips that you guys have successfully used and are sharing is way cool. Keeps us novices from eating up bunches of parts and time.
Thank you very much!
I use multiple engine/porting programs daily. I started in 1993 with SAE's attempt to rewrite Blairs into dos then Tom Turner made them his TSR's programs and I got them as soon as they were marketed (maybe 1995 or 6 or 7, don't remember) then got Mota, never liked it, then numerous others. I still use all of them except Mota because each one has something to offer. In early 2007 I leased ENGMOD2. This program is the best I'm aware of but the damn thing will drive you out of your friggin mind playing "what if", it is not for the beginner and most new users give up, start with a couple programs that are not as good but will get you exposed, yes they may have faults but will teach you some basics until you're ready to advance.
Venturi dividers will provide better roll on performance stronger all Throttle openings including mid-range less light switch
(https://i.postimg.cc/y3DVkkZ2/20241012-160940.avif) (https://postimg.cc/y3DVkkZ2)
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(https://i.postimg.cc/yDRx0FXV/IMG-2757.jpg) (https://postimg.cc/yDRx0FXV)
MY pictures did not load .????
IM not having any luck loading pictures from my phone or computer , If anyone wants to see pictures of the carbs text me and I can send that way. 702-858-9177
the pics are there. :toot: they loaded.
as said, un-ported un modified internals leave a lot of meat on the bone, i pretty much wanted to do that bike with strictly bolts ons, just because.
Did a short test with the Bassani pipes this afternoon. Didn't have the baffles packed and in yet, but I just had to try a short run. WOW! Quite the difference. Much less burbling around 5k, pulls harder and longer. Probably picked up 500RPM. It seems to want to be shifted about 9k now.
Can't wait to get the baffles packed and in so that I can play/test some more.
Didn't seem to help the mid range, but it really picked up up top.