I bought a chinese atv pretty sure it is a gy6 150cc or 200cc. I got it to start up and it ran good then when i went to start it again it made a grinding noise and would crank the engine until compression and then sort of stop and then keep cranking. I had a mate that was a motorbike mechanic and he checked the flywheel, starter clutch and the teeth and everything seemed to be in good condition I also took out the starter motor and it ran fine no grinding noise but when i put it back in the engine it just does the same grinding noise. Im not sure what it could be. If anyone knows what it could be please let me know.