Bro, I had the same problem before. bike cannot travel past 3.5 to 4rpm. my bike could start and can travel for about 10 to 15 minutes before it cuts off automatically and could not start again. I had to let it cool down say for about 5 minutes before i can start again.
if you have the same experience as i had, u can try changing your CDI as your circuit board aka cpu aka brain of your bike electrical system is damaged. i hv a spare CDI that i'm selling off at only $100 (retail price is $120 if not wrong). lastly, it can be because of your stator aka magnetic coil that is damaged.