Twin Spark +R Superhead 124cc bore and stroke kit for the XR100R and CRF100F improves spark efficiency and combustion. Largest valves in class, and the proven forged aluminum roller rockers are included in this top of the line bore kit. 3 SR series cam choices make this kit more versatile than any other on the market.

• Bore: 57mm  Stroke: 48.5mm
• Kit comes with SR-25 camshaft