I have a 1983 air cooled 250r, the piston is 71.50mm, head shaved .20 with aftermarket pipe. I bought a new carb and it seems to want to die all the way open and runs fine 3/4 of the way. The carb is a mikuni and I have a 360 main jet and 45 pilot jet. I sure hope someone can help I,m about to find a new owner for this thing.

 

is all your jets set properly is your spark plug good dose it get plenty of gas

 

The jets just screw in only way to adjust carb is air and idle screws on out side. The plug is fine I rode it over 5 hours and didn't foul, the color is light brown .