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Discussion Starter · #1 · (Edited)
New to the forum, been on for couple weeks actually. I’m out on oahu Hawaii. If any other R members here from the islands hit me up. 🤙🏾

Currently in the process of my 87 build.

ESR 363
350 ceo
Hotrods +4 stroker
Ported by Canebrake racing
Vforce reeds
UPP manifold
38mm keihin a/s
No airbox
Just waiting on my BB pipe from LED then I can finally get it running.
stock ignition
gonna be running on 108 octane race gas

Not sure if this is the right place to ask for help but:

any recommendations on where to start with jetting?

Also, with a stock ignition what’s the recommended spark plug for this build or do I just keep the br8es that i been running with the stock cylinder?

and last question, what Gearing is everyone running on their big bore? Right now im stock geared 13/39 and I run 18’s on the rear looking to do mostly mx/recreational riding.

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Aloha and welcome! Nice build!

I have a very similar engine setup, but I’m running a 39 PWK with a stock, open airbox. My jetting in MI (~500-800 ft above sea level) will probably be around 185 main, 55 pilot, DGH needle in the middle clip as a reference. Being that you’re in O’ahu (~4000 ft above sea level), you’re probably a little leaner than me.

You’re fine with the BR8ES, but gap it to .018”-.020” due to the weak OEM ignition.

As for gearing, I’ve liked 13/38 on my 310, but that’s with 20” tires. You’ll likely find that a 13-14 front sprocket with a 38-37 rear will work best.
 

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Discussion Starter · #3 ·
Aloha and welcome! Nice build!

I have a very similar engine setup, but I’m running a 39 PWK with a stock, open airbox. My jetting in MI (~500-800 ft above sea level) will probably be around 185 main, 55 pilot, DGH needle in the middle clip as a reference. Being that you’re in O’ahu (~4000 ft above sea level), you’re probably a little leaner than me.

You’re fine with the BR8ES, but gap it to .018”-.020” due to the weak OEM ignition.

As for gearing, I’ve liked 13/38 on my 310, but that’s with 20” tires. You’ll likely find that a 13-14 front sprocket with a 38-37 rear will work best.
Thanks for your help. I ended up just grabbing a 190 main and a 55 pilot just to get me going for now. Atleast I’ll be able to get it through it’s heat cycles. I’m still waiting on my bb pipe to come in. So I’m tryna finalize everything so when it finally comes in I can get it running.

I’ve never ran other sprockets yet on my stock cyl before the build. Might give a 14-38 a try.
 

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Discussion Starter · #4 ·
Aloha and welcome! Nice build!

I have a very similar engine setup, but I’m running a 39 PWK with a stock, open airbox. My jetting in MI (~500-800 ft above sea level) will probably be around 185 main, 55 pilot, DGH needle in the middle clip as a reference. Being that you’re in O’ahu (~4000 ft above sea level), you’re probably a little leaner than me.

You’re fine with the BR8ES, but gap it to .018”-.020” due to the weak OEM ignition.


As for gearing, I’ve liked 13/38 on my 310, but that’s with 20” tires. You’ll likely find that a 13-14 front sprocket with a 38-37 rear will work best.


So I finally got my LED pipe. Bike is running now. So I ended up running torco 112 leaded race fuel instead of 108 only because the 108 was Unleaded. I’m mixing my oil at 38:1 ish. My question is how bad does humidity affect jetting?
I’ve been trying to tune my pilot and started at 55 and it was way too rich and I just kept coming down finally to a 42 and 2 turns out on the air screw and seems to idle good with really good throttle response. I’m pretty much at sea level and Humidity ranges from I wanna say 50-80%. I haven’t done any plug chops yet, but right now with the 42 pilot if I pull the plug out after idling the plug is wet with fuel.
And yes I did reset my float height in my carb.
 

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That pipe from Arlan is awesome, is it not? He does some great work. You will love it. Humidity is a huge factor. You are trying to burn water. Believe me, I'm in S. Florida 60-90% all the time.
I wouldn't go any smaller than the 42. You will get a wetter plug at idle. But it should clear out quickly when you start to ride. What size main are you running.
 

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Discussion Starter · #6 ·
That pipe from Arlan is awesome, is it not? He does some great work. You will love it. Humidity is a huge factor. You are trying to burn water. Believe me, I'm in S. Florida 60-90% all the time.
I wouldn't go any smaller than the 42. You will get a wetter plug at idle. But it should clear out quickly when you start to ride. What size main are you running.

I love the pipe. It looks so sick, and it sounds amazing.

I ended up bumping up the pilot to a 45 I didn’t like the fact that I was going running such a small one. But it still seems a little bit rich. For the main I’m at a 188 I haven’t really gotten into dialing in the main yet, wasn’t going to till I figured out the pilot jetting. But I did take it for a ride and noticed that at about 3/4 throttle it sputters and doesn’t wanna go anywhere. So I feel like the main is really rich also.
 

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Discussion Starter · #8 ·
Did you do a leak-down test, prior to start up? What needle are you running and what clip position is it in?

Leak test passed.
And if any of this info matters: my compression is at 200psi. Did a uccr and if I did it correctly I’m at an 11:1 comp ratio.

If I roll on the throttle a little slower it pulls pretty good from low to midrange without cutting out or sputtering, but once I get any further than about 3/4 throttle, it’s sputters.

I wanna say I have a DGH needle in my carb. I took it out and it’s really hard to read it, I can see the DG but after that it’s hard to read it. and it’s set to the middle clip position.
 

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Discussion Starter · #9 ·
Did you do a leak-down test, prior to start up? What needle are you running and what clip position is it in?

Update. I dropped main to a 182 and pilot to back to the 42. Air screw 2 turns out. Rode it around for a good 15 min at various throttle ranges and when I pulled the plug out it was still a little wet, the insulation had a dark brown color and almost black on one side of the insulation.
At about 1/8 throttle it sounds and feels weird, it sounds like a very fast sputtering. 1/4 throttle to about 1/2 throttle, Mid range pulls really hard, then after that if I go 3/4 to wot it still sputters and sometimes clears out but not as bad as when I had the 188 main in it. I have a hard time identifying a lean sputter vs a rich sputter. But if I lug it in 5th or 6th and hold it WOT it’ll pull through the powerband smoothely. Only when I’m in the lower gears and try to go wide open it will want to sputter.
 

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It sounds like you are tuning in the right direction. Sputters are associated with a rich condition. Make one change at a time. Leave the main alone, drop the needle one position. take it for a spin. I have some info at work from Arlan on needle selection. I’ll check that out tomorrow. In the mean time I provided a link from Duncan Racing. This read would help me at times.

 

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Discussion Starter · #11 ·
It sounds like you are tuning in the right direction. Sputters are associated with a rich condition. Make one change at a time. Leave the main alone, drop the needle one position. take it for a spin. I have some info at work from Arlan on needle selection. I’ll check that out tomorrow. In the mean time I provided a link from Duncan Racing. This read would help me at times.

Thanks, wasnt sure If the sputtering was lean or rich. Thanks for clearing that up. I ordered more jets and different needles to try too. But until they come in I’ll try leaning out the needle and see what happens.
 
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