90cc Monster Big Bore Kit (QMB139) - Rolling Wrench

This is our more affordable (vs ProBld) monster big bore kit! If you are looking for the largest kit on the market, this is it! It's a true 90cc. Don't let the $30 Ebay and Amazon 100cc kits fool you.

This kit will convert your 49cc Chinese scooter, Kymco Agility or anything with the QMB139 engine to 90cc. The 90cc is as large as you can go with this engine. This kit is great quality . You won't find a nicer big bore kit. Remember you get what you pay for! The stock cylinder head will not fit. The cylinder head supplied in this kit is complete with larger valves and bigger ports, making it a performance head.

Big Valves and Ports:

Intake Valve: 21mm (Stock is 18.5mm)
Intake Port: 20.5mm (Stock is 18.5mm)
Exhaust valve: 22mm (Stock is 16mm)
Exhaust port: 19mm (Stock is 17mm)

This kit includes:

Piston

Piston Rings (not pre installed)

Cylinder

Performance Cylinder Head (Complete with big valves)

complete rocker box assembly

performance cam shaft (if you choose)

FREE STEP BY STEP INSTALL VIDEO!

 BECAUSE THIS IS A DOMED STYLE PISTON, BE SURE YOU HAVE A HEALTHY BATTERY. THIS IS A HIGH COMPRESSION KIT.

GY6 torque settings click here