Crankshaft with 16 tooth oil pump driven sprocket for 139QMB/QMAOriginal quality aftermarket crank for 50/90cc 4-stroke engines (GY6 50, 139QMB/QMA. The crank is pre-pressed with main bearings and rodGY6 engines are factory-fitted with 2 different versions of crank. The only difference is the oil pump drive cog on the right-hand sideThe old version, installed in almost all vehicles, has a 16 tooth cogThe new version has 22 teeth and is used in e.g.: Rex models. For added assurance, count the number of teeth on your cog and reference the image provided