KymcoForum.com

Hello , i am new here and have acquired an erly kymco mxu 300 with a carb. It had a blown head gasket that i replaced.it an ok afterwards but now it will start and then just stop after a few seconds. Every now and then it will start and then run as normal. I have checked compression which is good, double checked cam timing and valve clearances and pulled the rad cap when it actually does run to check if any leaks (plus a leak down test). The carb is clean and the fuel level in the carb is correct.
I am a bit lost and am wondering whether it is ignition related (new plug and ht cal checked for resistance). Can someone give any ideas? Also what purpose does
change gear control unit serve in the ignition circuit?
Any help would be gratefully appreciaated.
regards Hug