172cc cast or forged piston cylinder options for tailored performance and durability
Performance big valve head and camshaft for increased torque and acceleration
Pre-gapped 8mm exhaust studs and nuts for easy installation and reliable fit
NGK spark plug included for optimal ignition and engine performance
All required gaskets and small parts included for a complete DIY or professional build
Summarized by Shop
Here are links to each individual part 👇
172cc Cast Piston Cylinder - Rolling Wrench
172cc Forged Piston Cylinder – ProBld
GY6 61mm Performance Big Valve Head
GY6 Performance Camshaft – ProBld
NCY Performance Cylinder
NCY Performance Cylinder Head
GY6 Camshaft - NCY
Shorty Pro Clocking Flange
GY6 Scooter Spark Plug (Pre-gapp
Engine Displacement
172cc
Engine Design
4-stroke
Engine Type
Gas
Piston Material
Cast or forged (depending on kit)
Valve Head
Big valve head, 28mm/23mm with hardware
Camshaft
Performance cam, adjustable clocking flange included
Spark Plug
NGK included
Fits
QMJ157 Gy6 long case engines only, no engine boring required
Summarized by Shop
5.0
24 ratings
5
4
3
2
1
Installed the new cylinder and piston. Turned it over by hand and the original valves were leaking. No surprise really with a higher compression. Cleaned and ground the valves and we are getting close to 180 psi and it’s running great! Idles perfectly at very low RPM. Love it.
E
Eric · November 4, 2025
The Big Bore Kit that I ordered works flawlessly. Installation went smoothly and customer service is Top Notch. She even advised me that it may not fit in my GY6A Buggy, but I ordered anyways and it was perfect. Matt's videos are always helpful and on point with all aspects of the install. Will definitely purchase more from them for my new to me GY6B buggy. Possibly do a 232 Big Bore in the near future.
A
Anonymous · August 20, 2025
Good quality parts good service, the ruck definitely has more power and torque. Now it’s time to gear up.