Jump to content
Sign in to follow this  

PWK 39.5 jetting help. 93 KX250

Recommended Posts

I just installed a Keihin 39.5 PWK carb off a 91 KX500 on my 93 KX250

Looking for jetting advice.

68.50mm bore 265cc ported, stock pipe and silencer.

Share this post


Link to post
Share on other sites

You have a larger bore, which normally requires slightly leaner jetting. But the increased Bernoulli effect that a larger bore will cause if the carb stays the same size is likely cancelled out by the larger carb. So I would probably start with the stock jet sizes for your KX250 and work from there. I'll bet it's not really that far off.

Share this post


Link to post
Share on other sites

Well I just had it out today 54 degrees and 43% humidity.

It started with a N82M needle on the second from leanest groove, #60 pilot and 170 main, air screw 1.5 out.

First run mas extremely rich.

Second I put needle on the leanest groove and installed a #48 pilot ( it's all I had ) still 170 main.

Ran better but still fat.

Today I tried a 165 main witch helped a little and now a 160 main.

It runs ok but still fat in midrange, sorta almost struggles to come on pipe, maybe a leaner main would fix it?

But I would like advice on a leaner needle cause it's on its leanest setting.

This is it's current setting, N82M needle on leanest groove, #48 pilot, 1.25 air screw, 160 main.

I might try a 150-155 main.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×