Stumbling at 1/8 throttle

EDITT** it seems that no one makes bigger pilot jets for this model carb***

Hello Guys, I've really honestly tried for 2 days straight a few hours at a time to hunt down some of these pilots but bigger as stock are #35, im lookin for bigger sizes like 38 or 40 but for the life of me i checked Z1 enterprises, Jetsrus, Bike bandit. If someone could help me find a link for bigger pilot jets for these specific Carbs ( Keihin CV34) exactly it would be much appreciated. I tried my best to avoid making a useless post/thread but i tried my best guys. thanks

The issue still remains and i am open for any suggestions possible if i missed anything.

The issue:
I'm getting sputter from 0 to 1/8 throttle (hesitation). Mostly and 100% problem happens when rolling out of first gear from a dead stop

Analysis: Doesnt happen with slight choke on (is there a way to fix the baseline level of choke? maybe im going into the negatives and the choke DOES have to be enabled somewhat maybe like 2% on.)

What i did:
All o-rings have been replaced, carbs cleaned through sonic, new boots up front and back, using stock air box with the old air filter taped off (worked better than a new k&n) mixture screws are screwed all the way down to be seated lightly. Petcock Checked, Vacuum checked, Hoses are all in order. Needle is an after market with the clip on the lowest (richest) setting. Carbs are cleaned every passage way is open from what it looks like (very clean). there are 130 jets and 62 primary main jets. No other issues in any other throttle position or rpm range. Coils are good, eletrical is all sorted out, the issue seriously only happens 1/8 throttle at low RPMs. If anyone had an issue like this and has some sort of hat trick im open for suggestions, Do i have to live with always running the bike with 2% choke on?

I'm by no means an expert, but I think the general consensus is that bigger pilot jets than the stock #35 simply aren't available for the CV34s, nobody makes them. If your bike is stock, then the stock jet should work perfectly, which suggests that the fault might lie elsewhere.

MagnusMax wrote: I'm by no means an expert, but I think the general consensus is that bigger pilot jets than the stock #35 simply aren't available for the CV34s, nobody makes them. If your bike is stock, then the stock jet should work perfectly, which suggests that the fault might lie elsewhere.

thanks for reply/input i believe so as well, i was comming to this conclusion

check for air leaks in diaphragms.

Does this bike have stock air box and exhaust?

jumpship wrote: ... Keihin CV34...sputter from 0 to 1/8 throttle (hesitation). Mostly and 100% problem happens when rolling out of first gear from a dead stop
Analysis: Doesnt happen with slight choke on...mixture screws are screwed all the way down to be seated lightly...Needle is an after market with the clip on the lowest (richest) setting...issue seriously only happens 1/8 throttle at low RPMs....

Mixture screws should not be "seated," as they are designed to regulate volume of fuel mixture drawn into the combustion chamber via the intake port.

Adjustment of the mixture screws is an important part of the tuning process, especially for proper idle and smooth strong pull-away.

The default position of the mixture screws is usually provided in the service manual, and may be such as 1.5 or 2 turns out counterclockwise from lightly seated.





Good Fortune!

bountyhunter wrote: check for air leaks in diaphragms.

Does this bike have stock air box and exhaust?

4-1 Kerker with stock air box with the filter taped off. We checked the hats there was one small hole we fixed it though no difference

Patton wrote:

jumpship wrote: ... Keihin CV34...sputter from 0 to 1/8 throttle (hesitation). Mostly and 100% problem happens when rolling out of first gear from a dead stop
Analysis: Doesnt happen with slight choke on...mixture screws are screwed all the way down to be seated lightly...Needle is an after market with the clip on the lowest (richest) setting...issue seriously only happens 1/8 throttle at low RPMs....

Mixture screws should not be "seated," as they are designed to regulate volume of fuel mixture drawn into the combustion chamber via the intake port.

Adjustment of the mixture screws is an important part of the tuning process, especially for proper idle and smooth strong pull-away.

The default position of the mixture screws is usually provided in the service manual, and may be such as 1.5 or 2 turns out counterclockwise from lightly seated.

Good Fortune!

gonna try It out, Clymer's said the more in you go the richer,and the bike is definitely asking for fuel which is the only reason why i went all the way in. However ur right seated might be bad. I'm gonna try a few turns out on my break thanks for replies.

Please, Keep us updated!

jumpship wrote: ...Clymer's said the more in you go the richer,and the bike is definitely asking for fuel which is the only reason why i went all the way in....

CV34 carb has a vacuum operated slide, and does NOT have a manually operated slide.

The Clymer is likely addressing a manual slide carb with a pilot air screw, and not a CV carb with a pilot "mixture" screw.

The side-located pilot air screw on a manual slide carb allows more air into the fuel mixture as it's turned out counterclockwise, and less air into the fuel mixture as it's turned in clockwise.

In the case at hand, would start with 2 turns out from lightly seated.

Good Fortune!

Hmm might have to turn your head a bit LOL but here's what the manual said. I did find it funny that in would be rich... maybe I'm reading it wrong? I haven't tried the 2 turns out yet I'll let you know in a bit

You shouldn't need bigger pilots. Not available anyway.
Screw 2 turns out from lightly seated like Patton said. Factpry setting is 2.
Check for blockage at point #5 in Pattons diagram. Look for 3 holes in that position and you may have to poke them with a fine wire or bent pin. Often overlooked in a carb cleaning

JR wrote: You shouldn't need bigger pilots. Not available anyway.
Screw 2 turns out from lightly seated like Patton said. Factpry setting is 2.
Check for blockage at point #5 in Pattons diagram. Look for 3 holes in that position and you may have to poke them with a fine wire or bent pin. Often overlooked in a carb cleaning

Hmm good point. I hope it's as easy as turning them screws out

Here's what I did on my 1 hour lunch. I started at 2 open, and results were very similar, than I went to 4, got a bit better. And believe it or not I went to 6 turns out, and the moment I started her up and got on the bike the issue was resolved and i mean totally! But after riding around for like 10 minutes the trouble came back. And the idle would be normal but drop suddenly.

1.Because of the inconsistencies I'm thinking she probably needs a good clean in section 5 on each carb??

2. Do u think I should have rode around each time I made an adjustments on the screws? Cause I only revved the bike a bit to hear the hesitation and that's how I determined to keep backing out