Finally took my 250 Racer out for a good ride after being rebuilt again.

Went through 2 plugs because I got things running pretty rich right now, but beyond that here is the issue:

Bottom end loads up real quick and seems to sputter from off idle to about 1/4 throttle. Once you get to about 1/2 throttle things will clean up and it will run great.

Midrange and top end seems to be pretty crisp and real responsive.

Pilot jet is stock, Needle is on 3rd groove, 280 main jet. Pilot Air Screw is a little over 1 turn out.

Thanks in advance for any suggestion or advice!!

 

You should go up at least 2 sizes on the pilots and adjust the air fuel screw by holding the throttle open about 1/4 inch while the engine is running and listen to the engine as you adjust the screw. When you get the highest rpm out of it you have finished the adjustment!!![img]i/expressions/face-icon-small-wink.gif[/img]

 

So, are you saying it's not getting enough fuel at lower RPM?

I managed to foul 2 plugs while riding yesterday but I attributed that to mixing my gas pretty rich (about 20:1) and riding real slow through some real rough trails.