This one had a huge failure as well . Think it was run lean , dropped the head of the exhaust valve . Mushroomed the bottom of the spark plug ,also put a big whole in the piston . Bought a new lifan engine 163fml. up and running as of last Saturday . Moved the needle clip to the bottom in the carb . after my first 10 mile ride checked the plug and has color . Think there were vacuum leaks as well on the old engine . All looks good for now . This bike has aluminum wheels . Is that normal for Chinese bikes?