CRF300L'21-25 - 301cc Big Bore Kit

Developed for racing endeavors on a CBR300R, this 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 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 (+20%) and horsepower (+30%). 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
•     New, OEM Honda cylinder bored to match piston
•     Cometic head and base gaskets in custom thickness to optimize quench clearance
•     Upgraded Class 10 stud nuts

This kit should be installed by a professional mechanic or someone of similar experience following steps outlined in a service manual.

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.

Break-in recommendations for your 301 big-bore kit:
Break in is the final machining operation on the engine. It’s the process of mating the cylinder to
the piston rings and it ensures optimal performance and longevity. With the following protocol,
you can break in your new big-bore in about 30 miles.
We strongly suggest using Maxima Break-In Oil or another name-brand non-synthetic oil for
the first 100 miles before switching to a regular performance oil such as Maxima ProPlus.
For the first startup, run the bike in neutral until the cylinder is very warm to the touch (usually
2-3 minutes) while gently varying RPM to no more than half the rev limit, then allow the engine
to fully cool. A fan pointed at the motor will expedite this process.
Repeat this process three times, allowing the engine temperature to rise a little higher each
time. Finally, run the engine until it reaches full operating temperature. Since component size
changes with temperature, the goal of this heat-cycle process is to gradually bring the
components to operating tolerances.
Now it’s time for light-load riding; no more than 50% throttle or 6,000 RPM with plenty of RPM
variation. Ride the bike for 10 miles, then stop and allow the engine to fully cool.
Do this light-load riding once again, this time for 15-20 miles, with occasional and brief runs up
to full RPM.
Allow the bike to fully cool, check for leaks, and check the oil and coolant level. At this point the
engine can be considered properly broken in and ready to perform.