The biggest problem with high performance modifications to all these Chinese engines is the soft metal cranks.
The crank pin and wrist pin cannot stand the test of time.
I have eaten up a few on 47mm 70cc engines.
I’ve seen an engine with untrue crank snap the magnet right off from high rpm’s.
High torque..high rpm’s..high compression will take a Chinese crank out IF the engine is pushed hard continuously.