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  #1  
Old 03-29-2017, 02:24 PM
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Default Keihin PJ carb idle fix.

     

Hello,
I've found a fix of that carb which is well known of its problems because of the idle air circuit/choke combination design flaw. Was thinking about it because i've had enough with it not idling at all. Doing trail and enduro mostly it is hard not to keep the engine idling.

I've done a detailed article on another forum but it is in Greek. You could use google translator to help you out but watching the pictures you will get the idea behind it.

www.dirt-bike.gr •

Have done it to my CR '93 and I suppose it could be done to many other bikes using these carbs that are facing idle problems. The idea is to use a screw to adjust the slide position, it worked and now it also runs on 48 idle jet (55-58 before!) and need to go even lower 42/45 because it still runs a bit rich at low rpm. Though must get a slide with 6-7# cut away at some point to lean it a bit more down low. It is a fuss to get the initial idle adjustment because as you understand to adjust you have to lean over the carb, unscrew the slide cap, adjust then re assemble.
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Old 03-29-2017, 03:12 PM
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What?

So it prevents the slide from going all the way down? it holds it up a bit so the bibke will idle?


JErry
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  #3  
Old 03-29-2017, 03:36 PM
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Nice work, I like the idea but it would be nice if it was externally adjustable.
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Old 03-30-2017, 10:19 AM
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@JERRY311
Exactly, just like all other carbs (pwk,fcr, etc)

@cowboyona426
yup, thought about it as well but it cannot be done because of the carb body and slide design!
It is a down side tbh and bit of a hussle to adjust it but worth it in the end, bike runs much better at low rpms, need to source idle jets to make a few more test runs to make the mixture even better.
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Old 04-09-2017, 05:58 PM
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Quote:
Originally Posted by byronk View Post
@JERRY311
Exactly, just like all other carbs (pwk,fcr, etc)

@cowboyona426
yup, thought about it as well but it cannot be done because of the carb body and slide design!
It is a down side tbh and bit of a hussle to adjust it but worth it in the end, bike runs much better at low rpms, need to source idle jets to make a few more test runs to make the mixture even better.
Cool that you found a way to make it work. Many of these are in landfills now with people still riding the CR250 albeit with a PWK installed instead.
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Old 04-12-2017, 08:50 AM
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Quote:
Originally Posted by shrubitup View Post
Cool that you found a way to make it work. Many of these are in landfills now with people still riding the CR250 albeit with a PWK installed instead.
I spy a familiar name from TT, good to see you over in this corner of the interwebs.
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Old 04-14-2017, 04:32 PM
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Quote:
Originally Posted by cowboyona426 View Post
I spy a familiar name from TT, good to see you over in this corner of the interwebs.

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Old 07-11-2017, 01:46 PM
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Good idea. Easy to do too. It just takes some effort for the initial setup.
Greg
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Old 07-14-2017, 08:47 AM
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Update, after trying almost everything there are a few issues with that mod.

Firstly after the bike sitting for long time like a week or more and the fuel evaporates from the float bowl it is very hard to prime itself with fuel to start up. This also happens when rejetting or draining the fuel from the bowl. Even with the choke on it refuses to start, after many kicks and overflows by leaning the bike over, it then starts. After that it runs properly and starts every time.

Secondly, it runs rich when riding at low revs (slow trails) and it fouls the spark plug after about 2-3hours of riding, even with 38 idle jet at 2,5 turns out and using B7ES plug! Needle at 2nd from top clip position and this is with 30-35οC ambient temp. Might be something to do with worn out needle jet maybe and fuel passes through it, even though looking at it with the eye it does not look like to be much worn out.

Had enough with that carb, waiting for a PWK 36mm to try out, anyone knows what idle jet should begin with at sea level and 30-35oC ambient temp?
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Old 07-14-2017, 10:14 AM
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Bummer it didn't work out. The PWK seems to be the way to go.
Greg
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