these chinese 50cc 4stroke autos have the same engine in loads of models and one of the things they suffer from is tight tappets especially the exhaust valve clearance,so take the rocker cover of the front of the engine tunr the engine over until its on tdc on the compression stroke and check they have clearances,set the inlet valve to .05mm and the exhaust to .08 mm
adam bike doctor(of milton keynes motorcycle centre), February 2011
