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Ari Henning Signature Series

CRF 300L 301cc Big Bore Kit

CRF 300L 301cc Big Bore Kit

Regular price $749.99 USD
Regular price Sale price $749.99 USD
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This 78mm (+2mm) forged piston kit boosts the CRF 300L's displacement to 300cc and increases compression from 10.7:1 to 11.5:1 for better throttle response and power. Pairing this kit with our Stage 3 tune can result in an impressive 31+ horsepower and 22+ foot-pounds of torque, a 34% and 25% jump respectively. For the highest performance, opt for the Stage 4 tune and parts package, boosting horsepower by a reliable 46% and torque by 26%, for a total of 34+ horsepower and 22+ foot-pounds of torque - similar to the 350cc European dual sports.

This kit includes the piston, tool-steel wrist pin, circlips, Japanese-made ring pack, Cometic head/base gaskets in custom thicknesses to provide ideal quench clearance, and a new OEM cylinder with black or silver color bored to the piston size. Each piston/cylinder set is expertly marked with distinct serial numbers. All parts (except for the ring pack) are fabricated in the USA.

There are other, imported kits on the market that offer more displacement, but that comes at the cost of increased ring drag and piston rock. This kit was developed by CBR300R racer and YouTube host Ari Henning for his own personal race use, and as such it has been highly refined and proven completely reliable. Ari won several championships, set one lap record, and won dozens of races with this kit. Customers have even run this piston with turbos and put it in land-speed bikes. This same performance and reliability is available for your CRF300L.

Break In Recommendations


This kit should only be installed by a certified dealer or a person with access to a service manual. ECU tuning and compatible accessories should be used in conjunction with this kit. The rings come pre-gapped and new head stud nuts are included with this kit. 

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