301cc Big Bore Piston Kit

Originally developed for my racing endeavors on a CBR300R, this piston kit has dozens of race wins, two class championships, and one lap record to its credit. With tens of thousands street and off-road miles logged, this is a proven and reliable setup for improving your CRF's performance, capability, and fun factor.

This big-bore piston kit turns your CRF300L into a true 300 with an additional 14.8cc of displacement and bumps compression from the stock 10.7:1 to 11.5:1. When combined with a high-flow air filter, high flow velocity stack, CBR cams, performance exhaust, and proper tune, you get a massive increase in torque (+25%) and horsepower (+34%). Running our ported head increases performance even more. 

Expect faster acceleration, snappier throttle response, and easier highway cruising. See dyno chart and performance comparison below.  

This is a complete and comprehensive kit that includes: 

• Forged 78mm piston, 11.5:1 compression ratio
• Piston ring set, properly gapped
• Wrist pin and circlips
  
• Cometic head and base gaskets in custom thickness to optimize quench clearance
• Upgraded Class 10 stud nuts
• Click here for engine break-in guidelines

This kit requires boring your stock cylinder to 0.003" clearance with the piston and should be installed by a professional mechanic or someone of similar experience following steps outlined in a service manual. Proper ECU tuning and 91 octane (R+M)/2 (95 RON) gas is required. We offer 550 Performance ECUs and also have PowerVision flashes available. 

Warning: This product is for closed-course competition use only and is not intended for street use or use on public lands. This product is not legal for sale or use in California.