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KX 125 engine bog from idle- possibilities?

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My friend just called me for help. He has a 89 KX 125 and when he opens the throttle quickly form idle the engine bogs and will quit, if he rolls the throttle on slowly the engine will build up RPM's and it runs well if the RPM's are up.

He has tried cleaning the carb but no difference.

What are the possibilities?

the bike will idle fine, its just when the throttle is opened quickly

One more thing,

I went over to help him with his a/s adjustment,

I started the bike from cold and with the choke on - normal but,

after the bike warmed up and I noticed to keep the engine from hesitating with a quick blip on the throttle I could put the choke on and the engine would be much more responsive, with the choke off I could make the engine die with a quick throttle open

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He did take the jets "out" to clean correct?

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u have a clogged pilot jet if works better with choke on ... re-clean carb they can be tricky to get 100 % clean / debris free ... just a TINY piece of dirt etc can clog pilot

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definitely jetting issues
Pilot circuit, go clean it.

Carb was taken completely apart and cleaned twice - soaked in carb cleaner and blown out. Jets are clean

Float level is correct

i agree, (Jetting) any idea how i can get the recommended jetting for this carb, we don't trust the previous owners maintenance practices.

what we have:

NJ - 1st clip

153 - MJ

52 - PJ

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u have a clogged pilot jet if works better with choke on ... re-clean carb they can be tricky to get 100 % clean / debris free ... just a TINY piece of dirt etc can clog pilot

Thanks, we will clean the carb again - would like to have an idea where to start with the jet sizes

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jet your bike period. if he hasnt jetted it, it will not run right, because 100% are jetted wrong, as in not perfectly, so go through and make sure it runs crisp.

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Thanks, we will clean the carb again - would like to have an idea where to start with the jet sizes

What I mean is the 52 PJ sound reasonable for this 36mm PWK

This is a pretty extreme bog off idle

1200' elevation

50's temp

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check the compression. if it is more responsive with choke..its extremely lean. The pilot is jet is the major player off idle. I take a bic lighter and being careful not to burn my self....heat the jet with the flame very well. then use a bread wrap tie with paper removed to clean the center hole out...It works.

if it is clean then make sure the crank seals and intake boot and reeds are all in good order.

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