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Discussion Starter #1
I’m hoping to get a little advice. I just put a 35mm PWK air striker carb on today. It came new from Sudco with a 160 main and 48 pilot, dek needle. It was extremely rich on low end. I’ve gone to a 45 then a 42. It still has a slight stutter off idle and seems to be smoking more than usual in the idle to 1/4 throttle range. Not getting very much feedback from the air screw either. The stock pj was jetted at 160 main 45 pilot and was pretty good. Engine is tight with no leaks, compression right under 200 psi, stock pipe, rad valve, fmf silencer, vented airbox lid. Mixing VP110 and non ethanol pump gas @ 101 octane, 32:1 927. Elevation @ 275. Below 42 pilot seems small to me. Is it possible that the factory 4.5 throttle valve is too rich? I currently have it jetted with a 40 pilot, 162 main, needle clip in 3rd, and as @ 1-3/4. It still has a stutter off of idle. Any help would be greatly appreciated.
 

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If you are out on the air screw more then 3 turns and not getting any feed back then you still need to go smaller on the pilot.

before I would start “guessing” on what might be too small or assuming some other issue I would continue to go smaller on the pilot until you get feedback knowing it is leaning out at idle, and see if it fixes the stutter. You certainly are not going to hurt anything going smaller on the pilot while tuning.

if you go down another two sizes and still no effect on the air screw and still stuttering then I would start to look for other issues.

I’m at a high altitude but all the guesses I got on the pilot were way to rich. I kept thinking the same thing, “the pilot should not be this small”, turned out I was wrong. I finally got the right pilot jet in there and it runs fantastic.

going smaller on the pilot until you get feedback from the air screw will help eliminate it as a factor.
 

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Discussion Starter #3
If you are out on the air screw more then 3 turns and not getting any feed back then you still need to go smaller on the pilot.

before I would start “guessing” on what might be too small or assuming some other issue I would continue to go smaller on the pilot until you get feedback knowing it is leaning out at idle, and see if it fixes the stutter. You certainly are not going to hurt anything going smaller on the pilot while tuning.

if you go down another two sizes and still no effect on the air screw and still stuttering then I would start to look for other issues.

I’m at a high altitude but all the guesses I got on the pilot were way to rich. I kept thinking the same thing, “the pilot should not be this small”, turned out I was wrong. I finally got the right pilot jet in there and it runs fantastic.

going smaller on the pilot until you get feedback from the air screw will help eliminate it as a factor.
Thank you for the advice. I will go ahead and put a 38 pilot to see if i start to get more feedback from the air screw. The bike runs GREAT at anything above basically 1/8 throttle.
 

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Thank you for the advice. I will go ahead and put a 38 pilot to see if i start to get more feedback from the air screw. The bike runs GREAT at anything above basically 1/8 throttle.
my brother in law is in the same situation. I’m convinced that he needs a smaller pilot but he took it from me before I was done because he was going riding. It runs great but with some very minor hesitation right off throttle. It does not bother him, but it does me.

If you have to pull the carb to swap the pilot you may want to check your reeds. I don’t know a lot about reeds (except what I have read here) but guys on here say if they are worn or chipped on the edges that can be a problem.
 

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Discussion Starter #5
my brother in law is in the same situation. I’m convinced that he needs a smaller pilot but he took it from me before I was done because he was going riding. It runs great but with some very minor hesitation right off throttle. It does not bother him, but it does me.

If you have to pull the carb to swap the pilot you may want to check your reeds. I don’t know a lot about reeds (except what I have read here) but guys on here say if they are worn or chipped on the edges that can be a problem.
i pulled it down today and checked reeds to be sure. It’sa brand new rad valve and still looks new. I put a 38 pilot in. Cranks first kick with no choke and idles all day. If i gap it from idle,there is no hesitation... it revs out. Still has a little sputtter though right off idle when i rev it slow. Air screw will choke it down and die when tightened past 1/2 to close. Highest idle around 2-3/4 - 3, but no real change. All my experience tells me it’s too rich still, but I’ve never heard of going this low on a pilot. Only thing i new to do was order a 6.0 slide to lean that circuit out. Then maybe the pilot would be back where it should in the high 40’s. I was hoping that someone had some knowledge of that 35 air striker. Thank you for the feedback. Much appreciated.
 

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Discussion Starter #6
my brother in law is in the same situation. I’m convinced that he needs a smaller pilot but he took it from me before I was done because he was going riding. It runs great but with some very minor hesitation right off throttle. It does not bother him, but it does me.

If you have to pull the carb to swap the pilot you may want to check your reeds. I don’t know a lot about reeds (except what I have read here) but guys on here say if they are worn or chipped on the edges that can be a problem.
What is his carb and current jetting out of curiosity?
 

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What is his carb and current jetting out of curiosity?
the bike is new to him so we really have no idea what if any engine work has been done. I have never looked at the reeds (mistake) I should have checked compression just for the sake of knowing but I didn’t.

he is running the 86 PJ 34 mm carb. Open top air box and FMF pipe. We are at 4200 ft elevation. It currently has 45 pilot 155 main needle on 3rd clip.

I’m certain it needs a 42.

if you are getting feedback with the 38 (which sounds really small for your altitude) have you tried lowering the needle

I don’t know what you mean by a 6.0 slide, that’s new jargon for me.

I run a 38 PWK with a ported motor 185 compression high flow intake and custom cone pipe and my pilot is 48 165 main needle 3rd clip.
I’m also at 4200 ft.
 

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Discussion Starter #8
the bike is new to him so we really have no idea what if any engine work has been done. I have never looked at the reeds (mistake) I should have checked compression just for the sake of knowing but I didn’t.

he is running the 86 PJ 34 mm carb. Open top air box and FMF pipe. We are at 4200 ft elevation. It currently has 45 pilot 155 main needle on 3rd clip.

I’m certain it needs a 42.

if you are getting feedback with the 38 (which sounds really small for your altitude) have you tried lowering the needle

I don’t know what you mean by a 6.0 slide, that’s new jargon for me.

I run a 38 PWK with a ported motor 185 compression high flow intake and custom cone pipe and my pilot is 48 165 main needle 3rd clip.
I’m also at 4200 ft.
I’ve really been reading up on these carburetors.... trying to diagnose my problem. I’ve learned that the throttle valve cut away controls mostly the same circuit as the pilot jet.... I never even knew these made a difference in jetting) This 35 pwk air striker came with a 4.5, which is the richest one i believe.
At $75 a pop, i really didn’t want to go experimenting with them if it was something else. I didn’t have this issue with my other 2 carb’s (stock 34 PE and stock 34 PJ).
It runs great really...i just know it’s not right. I may go ahead and order a 6.0 slide, which should lean that circuit back out and i can richen up the pilot. I think the 38 air striker come with a 7.0 valve.... for reference.
 

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I’ve really been reading up on these carburetors.... trying to diagnose my problem. I’ve learned that the throttle valve cut away controls mostly the same circuit as the pilot jet.... I never even knew these made a difference in jetting) This 35 pwk air striker came with a 4.5, which is the richest one i believe.
At $75 a pop, i really didn’t want to go experimenting with them if it was something else. I didn’t have this issue with my other 2 carb’s (stock 34 PE and stock 34 PJ).
It runs great really...i just know it’s not right. I may go ahead and order a 6.0 slide, which should lean that circuit back out and i can richen up the pilot. I think the 38 air striker come with a 7.0 valve.... for reference.
Well that is news to me. Having learned that makes me wonder why one slide over the other?

another question: is a “rich slide” and a small pilot more or less desirable and under what conditions, or is the opposite true?

And if the come with different slides how would anyone know what one is best for there build?

I guess I have some reading to do???

it seems odd that ia “bigger” carb like a 38 comes with a leaner slide then a “smaller” carb Like a 35. Regardless this certainly seems like it could be your issue.

It’s weird to me that this issue is not discussed more often.
 

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Discussion Starter #10
Well i just ordered a #6 slide and a couple different needles. (dgh and cel). I’ll give it a go again when they come in and post back in case someone else is ever in this situation. Thanks for the feedback and advice so far.
 

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I’m hoping to get a little advice. I just put a 35mm PWK air striker carb on today. It came new from Sudco with a 160 main and 48 pilot, dek needle. It was extremely rich on low end. I’ve gone to a 45 then a 42. It still has a slight stutter off idle and seems to be smoking more than usual in the idle to 1/4 throttle range. Not getting very much feedback from the air screw either. The stock pj was jetted at 160 main 45 pilot and was pretty good. Engine is tight with no leaks, compression right under 200 psi, stock pipe, rad valve, fmf silencer, vented airbox lid. Mixing VP110 and non ethanol pump gas @ 101 octane, 32:1 927. Elevation @ 275. Below 42 pilot seems small to me. Is it possible that the factory 4.5 throttle valve is too rich? I currently have it jetted with a 40 pilot, 162 main, needle clip in 3rd, and as @ 1-3/4. It still has a stutter off of idle. Any help would be greatly appreciated.
Unfortunately SUDCO will not properly Jet a carburetor for any model, let alone a 250R. They basicly toss any jet combinations, unless you specify the jets you want and pay a very high added fee.

Proper slide Numbers for a 250R are 6-7, not 4.5. At 4.5 that is way off what the 250R needs. When installing the 6 or 7 slide, go up on the Pilot to 48. Typically on an OEM stock cylinder, with the components you detailed, this is a good starting place for jetting a 35MM carb:

160-165 Main
46-48 Pilot
DGH needle on 3rd clip
#6 or #7 slide
AS at 1 1/2 out
BPS at 2 1/4 out

Carlos
 

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Discussion Starter #12
Unfortunately SUDCO will not properly Jet a carburetor for any model, let alone a 250R. They basicly toss any jet combinations, unless you specify the jets you want and pay a very high added fee.

Proper slide Numbers for a 250R are 6-7, not 4.5. At 4.5 that is way off what the 250R needs. When installing the 6 or 7 slide, go up on the Pilot to 48. Typically on an OEM stock cylinder, with the components you detailed, this is a good starting place for jetting a 35MM carb:

160-165 Main
46-48 Pilot
DGH needle on 3rd clip
#6 or #7 slide
AS at 1 1/2 out
BPS at 2 1/4 out

Carlos
Thank you very much for that information. I am learning the hard way. The next mods i do to this bike.... will be coming from you.
 
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