Hello, i have a px200 engine with cilinder bored to fit a 210cc malossi piston, with a SIP performance exhaust, 24.24. carb with 50/100 idle jet and 116 main jet, while running at 70km/h aprox i felt like the piston seized a little, when opening the cilinder everything was good and didnt have any marks of a seizure, today it happened the same.
i don't know if it's part of the problem... but i've got a completely stock 200cc engine and it has a 116 main jet in it. it seems with a 210cc malossi piston, a sip performance exhaust , and a 24/24 carb - a 116 main jet could be too small. have you tried a bigger main jet?