Friend just bought a well used 250sx. It seems to run very rich, little smoke and wants to foul plugs and "surge".

Sounds like jetting to me, but looking for info from someone who knows.

 

I dont rember a 250SX, was there one? Anyway if it is blue smoke then it is oil, black smoke can be fixed by taking the carb off and with the float bowl off and the carb upside down just bend the floats until they are level. Joe

 

Yes there was a 250SX!
I had a 85 ATC250SX

It was awesome in its day

Rdogg