Carburetor Help Please

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Carburetor Help Please

Postby doakley » 03:07 pm Aug 01 2018

I'm having a cold cranking problem that I cannot seem to resolve. Bike is a '99 220, weisco piston, rechromed cyl, clean KIPS, stock carb, compression 160 psi. New jet block gasket. Won't start cold. After the first crank it will restart 1st kick, even before warm up. But that initial start of the day is a no go.
Acts sorta like it is flooded. It did not do this when I first got it, was a reliable 1-3 kick cold start then. All I've done is raise the idle a bit. Don't recall the jetting but 145 and 42 I think. Point is, I haven't changed the jets. Air screw is 1.5 out. New float valve with new viton (rubber) tip. Float height checked.

Installed my buddy's 35mm carb off his kdx200, and it cranks 1st kick again with his carb. Doesn't seem to matter which slide is in his carb, his or mine from the 220 carb. Seems pretty clear something is wrong with my carb. Question is...what? I'm out of ideas. Can the choke system be faulty? It looks clean and undamaged. Again it cranks flawlessly hot or even slightly warm, just not cold. Only exception is it often cranks cold right after I've disassembled, cleaned and reassembled . Not always though.
I need some experienced feedback before I just throw up my hands and buy a new carb!
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Re: Carburetor Help Please

Postby Jason » 07:02 pm Aug 01 2018

What is your starting technique? (choke, amount of throttle open)

Is it warmer now than when you were having good success before?
Thank you, Julien D for all your hard work!

PLEASE! Do not "dip" PWK Keihin carbs in Berryman's to clean them! It will damage the internal o-ring (jet block gasket).
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Re: Carburetor Help Please

Postby doakley » 08:24 pm Aug 01 2018

First start, choke pulled, just a crack of throttle, maybe 1/8th? Haven't changed technique. No change in outside air temp. This has been going on for some time, like well over a year.
What really made me decide it must be some unrecognized carb problem is the thing cranks great when I swap carbs.
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Re: Carburetor Help Please

Postby Jason » 08:31 pm Aug 01 2018

Did you compare float height on the two carbs?
Thank you, Julien D for all your hard work!

PLEASE! Do not "dip" PWK Keihin carbs in Berryman's to clean them! It will damage the internal o-ring (jet block gasket).
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Re: Carburetor Help Please

Postby david » 08:53 am Aug 02 2018

I would think it has to be a restriction in your choke circuit.
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Carburetor Help Please

Postby pumpguy » 11:24 am Aug 02 2018

Does the choke knob stay up when pulled?

I've had an on-and-off problem with the choke knob not staying up.

The zip tie trick around the choke rod boot usually works to hold the rod up, but then I'll go back and when I pull the choke up, it won't click into it's detent to stay up. Snipped off the zip tie and it stays up. Some time later try again and it won't stay up. Add zip tie again .......... I suppose I need a new choke assembly, but even with a new assembly, I'll probably have to add a zip tie again at some point.
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Re: Carburetor Help Please

Postby John_S » 12:45 pm Aug 02 2018

My guess is the choke circuit (considering that the other carb worked right away) and on yours I don't imagine you're using the choke for the second start up. Do you have to bump start it to get it going when cold? If it were mine I would:

1) Remove the choke and run a pipe cleaner, or long jet cleaner through the circuit and then blow compressed air down the chute and also through the hole in the back of the carb that leads to the choke. Those V shaped air compressor nozzles with the rubber tip are perfect for that.
2) Install a different pilot jet, even if its the same size.
3) Install a new spark plug gapped to spec.
4) Remove the spark plug boot, snip a 1/4" off of the wire, and reinstall.
5) Adjust the air screw to 1 turn out for a few kicks and then 2 turns out for few kicks when the engine is cold. *I would do this first since its the easiest
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Re: Carburetor Help Please

Postby doakley » 10:36 pm Aug 02 2018

Float height was almost identical on the two carbs. Choke knob stays up and appears to work correctly. I've sprayed carb cleaner thru the choke passages and compressed air. Have not put anything solid (wire, pipe cleaner, etc) through them. Certainly willing to try.

I like the idea of switching pilot jets. Maybe I'll swap jets from the other carb at least as a test.
Guess you are thinking weak spark on the plug wire cut off? Worth a try but that wouldn't explain why it cranks so easily with the other carb I don't think. Already tried multiple new plugs with no effect.
Other thing I haven't tried is swapping out the choke knob assemblies between the two carbs. I'll do that too.
Thanks for the input for you guys.
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Re: Carburetor Help Please

Postby Jason » 02:00 am Aug 03 2018

doakley wrote:Float height was almost identical on the two carbs. Choke knob stays up and appears to work correctly. I've sprayed carb cleaner thru the choke passages and compressed air. Have not put anything solid (wire, pipe cleaner, etc) through them. Certainly willing to try.

I like the idea of switching pilot jets. Maybe I'll swap jets from the other carb at least as a test.
Guess you are thinking weak spark on the plug wire cut off? Worth a try but that wouldn't explain why it cranks so easily with the other carb I don't think. Already tried multiple new plugs with no effect.
Other thing I haven't tried is swapping out the choke knob assemblies between the two carbs. I'll do that too.
Thanks for the input for you guys.


I am curious on the choke assembly swap. :hmm: :please:
Thank you, Julien D for all your hard work!

PLEASE! Do not "dip" PWK Keihin carbs in Berryman's to clean them! It will damage the internal o-ring (jet block gasket).
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Re: Carburetor Help Please

Postby doakley » 08:57 am Aug 03 2018

Me too. Think I’ll start there . I’ll report back. Unfortunately it may be a while. Due to a little medical procedure I don’t think I can kick it right now.
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Re: Carburetor Help Please

Postby doakley » 07:39 am Aug 09 2018

Update on cold cranking. I cleaned the pee out of the choke assembly, passages, etc. put in yet another new plug just for grins, and it has been cranking on the first kick consistently for the last 4 days! Hoping there was some blockage in the choke after all and the problem is solved. Feel pretty lame because I thought I had cleaned everything before but perhaps not. I’ll report back if the problem rears it’s ugly head again. Gotta’ love the help you get from this group.
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Re: Carburetor Help Please

Postby Jason » 09:54 am Aug 09 2018

Huh, new spark plug the whole time. :hmm:

:busted:

I am glad it seems to have been repaired. :bravo:
Thank you, Julien D for all your hard work!

PLEASE! Do not "dip" PWK Keihin carbs in Berryman's to clean them! It will damage the internal o-ring (jet block gasket).
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Re: Carburetor Help Please

Postby doakley » 07:00 pm Aug 10 2018

I don’t believe it was the plug. I’ve put in multiple new plugs in the past with no improvement. I’m pretty sure there was something in the choke passages that I had not adequately cleaned.
Whatever, it continues to crank on the first kick so I’m a happy camper at the moment.
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Re: Carburetor Help Please

Postby Jason » 07:59 pm Aug 10 2018

I was just being a dork. :mrgreen:
Thank you, Julien D for all your hard work!

PLEASE! Do not "dip" PWK Keihin carbs in Berryman's to clean them! It will damage the internal o-ring (jet block gasket).
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