i have a dellorto side draft that was on my sp 12a had 147k miles when i lost rear rotor compression. when i pulled my motor to replace it with a recently purchased low miles motor i noticed the rear housing exhaust port was very white and the front was black. im assuming from general knowledge that my rear housing was running leaner than the front hence the failure. i am running two different sized jets front was 220 and the rear was 230 if i remember correct.
im curious on some input i would like to keep the motor lasting as long as i can this time around.