Going to a CR shim gasket will make it a bit higher than 185-205psi cranking compression. I have an OEM ATC head gasket & stock 86 head on a non ported 66.75mm 88-89 cylinder with a hotrods LR crank & its just a hair over 200psi according to my snap-on compression gauge.
Also the head might be bored alot my 254cc's head was bored to 23.5 cc i am pretty sure it has oem cdi and it is super hard to kick over it also had a cr head gasket i am 160lbs and i can jump on the kicker and it wont turn over.
23.5CC's is not a High Compression dome for an OEM cylinder at 67.50MM bore. Something else is not correct; possibly squish is set extremely low. The statement "i can jump on the kicker and it wont turn over" is very troubling, not good!
I have 88 with ct 310. When mine wanted to fire, gave kick back and was being difficult, it was a combination of a bad cdi and fuel. Carb was lean and new cdi helped not kick back. The carb being lean was biggest issue. They tend to be very picky about fuel, oil, air mix and ratios. At least in my experience.
mr lee try to stay away from the aftermarket cdi.makes your machine run like crap and alot of kickback maybe a member will have one they can sell you or you can find a used oem cdi.take care and good luck.