Just thought this piece of information might be useful to other members.
I have fitted a early MC 18 motor to a stockman superkart and decided to use a PGM 11 as it was available at the time. The motor would start but never went well and was down on power with the front cylinder running cooler the than the back.
I never new exactly what model bike the engine came from and only had the engine number to roughly find out the age, early rather than a late build engine.
I eventually sourced a matching flywheel, pickups and PGM11.
I noticed that the sourced flywheel was of a smaller diameter than the one already fitted in the motor, also the pickups/sensors had a longer magnetic tip to reach the ignition points on the flywheel. As the ignition is sensed from the outside of the flywheel, the outside of the smaller flywheel will run slower than the larger one thus affecting the ignition timing at a given engine speed.
when the new smaller flywheel was fitted engine performance was greatly impoved with engine revs exceeding 12000 rpm.
Track test next .
I hope the above information is of use to those who are planning to chop different motors to make a good one, watch out for the flywheels.
Happy racing everyone
Owen
New Zealand

I have just replace the flywheel off my early MC18 motor,