I rebuilt the top end on my 99' KX250. It starts but only runs at hig RPM with the choke on. Once the chock is off it will not run or idle. You have to keep the throttle active to keep it running. Sounds like carb to me. Any input would be appreciated.

 

Yeah it does sound a lot like a carburetor problem.

Sure you didn't get any dirt in it when you removed the reed cage? That stuff will clog a jet pretty fast

 

Welcome to KF

Yeah could be as simple as cable adjustment. Back track and take a look at the boot, adjustments, etc.

 

Do all the basic carb cleaning stuff, check needle position. Maybe a cracked reed or a simple as the rubber boot being ripped between the reed cage an carb. With a boysen cage it's real tight and usually tear after awhile.

 

Sounds like a bad reed valve! But check all the simple stuff before you buy a new one.