I just rebuilt the top end on a 1983 ATC110. (.25MM over piston). I had a local shop bore the cylinder and
rebuild the head (cut valve seats, ream new valve guides, etc.). I put maybe 10 minutes on the new
engine. I am fairly confident that the carb is working properly, as I have cleaned it. The problem is that the motor runs rough (smokey exhaust), won't idle and when I try to adjust the fuel screw, it
is very erratic. The plug is black. I did a compression check and only had about 130-135 PSI (manual says 155 PSI is minimum). I added some oil through the spark plug hole and the compression increased to about 150 PSI.
Do you think I should tear the top end down and re-check all of the clearances? Could I have a leak somewhere else? Something is not right or it would idle and the fuel screw adjustment process would not be erratic. Your help is greatly appreciated .

Thanks,

Mat