High Compression/High Altitude GY6 171cc/172cc Scooter Big Bore Kits (FITS QMJ157)

This is our High Compression/High Altitude kit. This kit will come with a domed style piston. This raises the compression ratio. This is a must if you ride in an area that is 3000 feet or more above sea level. The higher you go in elevation, the more your compression is lowered. You can install this kit in a sea level engine no problem. Just know you will need an high torque starter and performance starter clutch. The high altitude people won’t need those parts. We have spent years testing and selling other kits. Some things we liked and others we didn't. We pieced this kit together with the best of the best materials (rings, gaskets, springs, and metals). This 171cc kit (or as some call it 172cc) is a no case boring big bore kit, unlike some others on the market. It's the largest big bore kit you can do on the GY6 A motor (Chinese GY6 QMJ157). Our 61mm kit is a drop in kit. Others on the market are not and will require engine case boring. Like they say “there is no replacement for