Honda ST90 Pit Bike Engine Adapter Kit

Convert your 1973-1975 Honda ST90 chassis to replace the original 89.5cc engine to a bigger, more modern pit bike style engine. Link to video instructions ship with the product. Tested on 125cc, 140cc, and 212cc pit bike engines. 

We've tested these in hard riding conditions with a 212cc 5 speed Zongshen engine. 

Convert your 1973-1975 Honda ST90 to a modern pit bike engine with our Honda ST90 Pit Bike Engine Adapter Kit. Designed for easy bolt-in installation—no welding required. Our 2mm thick adapter brackets ensure durability, we've thrash tested these adapter brackets on a 190cc 5 speed swapped Honda ST90. 

Fits 125cc, 140cc, and 190/212cc and other pit bike engines (minor clearancing may be required). 

Kit includes:

• Two laser cut engine adapter brackets
• All necessary hardware and shims
• Video installation instructions

Notes: Slight clearancing may be required on the adapters for certain engines/transmission configurations. Pit bike style exhaust/foot pegs required.

Photo: Honda ST90 with Zongshen 190cc 5 speed engine installed with thumper exhaust and pit bike foot pegs.