GY6 63mm 180cc-205cc H20 Big Bore Kit - ProBld

If you want to max out your GY6 QMJ157 cylinder, it doesn’t get any better than this! 63mm is the largest you can go on a GY6A(54mm stud spacing). This does require your cases to be bored out to make this bad boy fit. We have case boring tools if you need one CLICK HERE. Want to go big time and make your GY6 a 205cc? You will need a few parts to make that happen: Our 8.2mm stroker crank CLICK HERE,  a longer 94 link timing chain CLICK HERE, longer timing chain tensioners CLICK HERE, longer studs CLICK HERE, a low profile timing chain tensioner CLICK HERE,  high volume oil pump CLICK HERE, decompression big valve head with cam CLICK HERE, high torque starter CLICK HERE, and heavy duty starter clutch CLICK HERE. We definitely don’t recommend using the stock crank unless you purchase a good quality stock stroke crank. This cylinder requires a 6mm spacer (CLICK HERE) to be installed between the cylinder and engine case when using a 8.2mm stroker crank. We machined the 2V piston skirt to w