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 displacement“.

Another cool thing is the piston ring end gaps have been set and installed into the cylinder. This eliminates a ton of work and liability on your end. Easy peezy! For the money, this kit flat out rocks! We even have an install video! We would recommend adding a performance camshaft and big valve head to the kit for max power! And if you want to take it one step further, you can add the forged piston option for better strength and durability. We even have the option of adding the performance big valve head and performance cam shaft! You can even add a performance carburetor, but it’s not a necessity CLICK HERE!

**PISTON RING GAPS HAVE BEEN MEASURED AND PRE-INSTALLED ONTO THE PISTON, THEN INSTALLED INTO THE CYLINDER. DO NOT REMOVE THE PISTON FROM THE CYLINDER, THIS CAN RESULT IN BENDING THE RINGS DURING RE-INSTALLATION, AND REQUIRE YOU TO PURCHASE NEW RINGS. THIS IS A LUXURY SERVICE YOU WILL NOT GET IN OTHER KITS. SLIDE THE PISTON DOWN JUST FAR ENOUGH TO INSTALL THE PISTON PIN, WITHOUT EXPOSING THE RINGS**

You may find other kits for half the price online but note, they are made in China. This kit is made in Taiwan and there is a HUGE difference in quality.

THIS KIT HAS 54MM STUD SPACING (GY6 A)

ADD A WIDE BAND O2 SENSOR KIT TO MAKE TUNING A BREEZE CLICK HERE!

**THERE ARE NO RETURNS ON PERFORMANCE PARTS**

ATTENTION BUGGY OWNERS: WE HAVE NOT PERFECTED ALL THE GY6 ENGINE MODELS IN THE BUGGIES TO KNOW IF THIS KIT WILL FIT OR NOT. BUY AT YOUR OWN RISK. THE MAIN PROBLEM THAT OCCURS IS THE 2 SMALL OUTER BOLTS NOT MATCHING UP.

FREE INSTALL VIDEO BELOW: