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301cc Complete Big Bore Kit
301cc Complete Big Bore Kit
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Currently out of stock. We expect to have more kits assembled by late March. Please contact us to pre-order.
Originally developed for my 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, hi-flow velocity stack, CBR cams, performance exhaust, and Stage 3.0 ECU tune, you get a massive increase in torque (+25%) and horsepower (+34%). Throw on a CNC ported cylinder head and Stage 3.5 ECU tune for even more gains (+30% torque and +39% horsepower).
Expect faster acceleration, snappier throttle response, and easier highway cruising. See dyno charts 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
- Click here for engine break-in guidelines
This kit 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.
Don't hesitate to buy this kit. Ari is a true professional and has put together the most cost effective way to provide real power gains on the CRF300 platform. Even though this bike will never quite get into KTM, Beta, Husky territory power wise, I'm really excited to be not as far behind all while doing normal services at manageable intervals. Less work, more riding!
Very nice power modification. Bike feels great to ride now.
I'm 6'3" 250. Mods to the bike before:
Full yosh rs4, 550Performance velocity stack, air lid, filter, and stage 1 tune.
47t rear sprocket. WITH THE OLD MODS: Bike was peppy, but fell off hard in upper rpms. I ride a lot of wheelies. Was easy to clutch 2nd, 3rd, with the bike struggling with 4th.
WITH THE BBK, CBR CAMS, AND 550PERFORMANCE STAGE 3 TUNE:
I don't know what to say other than the bike is a completely different animal. It's got much much more grunt down low and it pulls clean to the top. Whilst it has so much more torque down low it is still very smooth and the on/off throttle response isn't choppy nor is the engine braking harsh at all. The bike easily clutches up in 4th and 5th for wheelies. EASILY.
Having so much more torque compared to stock allows me to put the bike where I want more efficiently. What I'm saying is that I don't have to tax the bike nearly as hard with high RPMs, clutch work, and wear on the transmission as I did before. I don't need to downshift nearly as much as there is available to work and not a hole in the power. I see this as a modification that will lend to the reliability of these other components. That being said, when you do ride it hard it rips. Feels like a totally different bike in a great way.
THIS IS HANDS DOWN THE BEST MODIFICATION I'VE DONE TO THE BIKE AND WELL WORTH THE PRICE.
Installation is tedious just in taking everything off to get to the head, etc, but it's easy work. Installation of the bbk and cams is easy. Timing is super easy on this bike. End result is worth the job.
The bike rips now. The imagined potential we've all felt and wanted out of the CRF300L has absolutely been achieved in this kit/combination and tune.
Absolutely recommend.
Awesome kit, not too bad to install. Airbox, fairings and all the bolted on crap took much longer then the actual Big bore cylinder install. Ari shipped out very quickly , The Rally is now halfway decent on power, especially on the upper end. This will help out tremendously on my next cross country adventure!
Here’s the short story: I highly recommend Ari Henning’s 301cc Complete Big Bore Kit for the Honda CRF300L, and Ari’s customer support is as good as his products.
After progressing from a KLR650 ADV bike to a Husqvarna Te630 and then a BMW F850 GSA, I decided I like the smaller bikes more and I downsized to a Honda CRF300L Rally. I was aware of its faults, but the basic platform was good—wind protection, weight, ergonomics, etc. The stock ECU tuning was horrible, at least in California. The on-off throttle response was like a light switch, and actually dangerous, so I started with a 91 octane ECU from 550Performance, which was a huge improvement, so much so that I began reading about its other products, which included Ari Henning’s Big Bore kit, which I decided to get. These changes transformed the engine. It delivers the extra power as advertised, but the engine is still as smooth as stock (smoother than my BMW). It doesn’t feel high-strung or like it has to be wrung out to get the power. I’m 200 pounds in gear, and the bike will pull sixth gear on hills. I changed the countershaft sprocket from the stock 14T to a 15T and also like this change for all gears. First gear is still usable for picking your way along slowly when you need to, and it will still pull sixth gear uphill. Fifth gear is actually nicer on the road and for hills because the engine doesn’t have to rev so much.
Other changes to complete the bike and make it fit include Precision luggage racks, Seat Concepts seat, lowered footpegs, skid plate, new handlebar and controls, and an Atlas throttle lock.
Don't hesitate to buy this kit. Ari is a true professional and has put together the most cost effective way to provide real power gains on the CRF300 platform. Even though this bike will never quite get into KTM, Beta, Husky territory power wise, I'm really excited to be not as far behind all while doing normal services at manageable intervals. Less work, more riding!
Very nice power modification. Bike feels great to ride now.
I'm 6'3" 250. Mods to the bike before:
Full yosh rs4, 550Performance velocity stack, air lid, filter, and stage 1 tune.
47t rear sprocket. WITH THE OLD MODS: Bike was peppy, but fell off hard in upper rpms. I ride a lot of wheelies. Was easy to clutch 2nd, 3rd, with the bike struggling with 4th.
WITH THE BBK, CBR CAMS, AND 550PERFORMANCE STAGE 3 TUNE:
I don't know what to say other than the bike is a completely different animal. It's got much much more grunt down low and it pulls clean to the top. Whilst it has so much more torque down low it is still very smooth and the on/off throttle response isn't choppy nor is the engine braking harsh at all. The bike easily clutches up in 4th and 5th for wheelies. EASILY.
Having so much more torque compared to stock allows me to put the bike where I want more efficiently. What I'm saying is that I don't have to tax the bike nearly as hard with high RPMs, clutch work, and wear on the transmission as I did before. I don't need to downshift nearly as much as there is available to work and not a hole in the power. I see this as a modification that will lend to the reliability of these other components. That being said, when you do ride it hard it rips. Feels like a totally different bike in a great way.
THIS IS HANDS DOWN THE BEST MODIFICATION I'VE DONE TO THE BIKE AND WELL WORTH THE PRICE.
Installation is tedious just in taking everything off to get to the head, etc, but it's easy work. Installation of the bbk and cams is easy. Timing is super easy on this bike. End result is worth the job.
The bike rips now. The imagined potential we've all felt and wanted out of the CRF300L has absolutely been achieved in this kit/combination and tune.
Absolutely recommend.
Awesome kit, not too bad to install. Airbox, fairings and all the bolted on crap took much longer then the actual Big bore cylinder install. Ari shipped out very quickly , The Rally is now halfway decent on power, especially on the upper end. This will help out tremendously on my next cross country adventure!
Here’s the short story: I highly recommend Ari Henning’s 301cc Complete Big Bore Kit for the Honda CRF300L, and Ari’s customer support is as good as his products.
After progressing from a KLR650 ADV bike to a Husqvarna Te630 and then a BMW F850 GSA, I decided I like the smaller bikes more and I downsized to a Honda CRF300L Rally. I was aware of its faults, but the basic platform was good—wind protection, weight, ergonomics, etc. The stock ECU tuning was horrible, at least in California. The on-off throttle response was like a light switch, and actually dangerous, so I started with a 91 octane ECU from 550Performance, which was a huge improvement, so much so that I began reading about its other products, which included Ari Henning’s Big Bore kit, which I decided to get. These changes transformed the engine. It delivers the extra power as advertised, but the engine is still as smooth as stock (smoother than my BMW). It doesn’t feel high-strung or like it has to be wrung out to get the power. I’m 200 pounds in gear, and the bike will pull sixth gear on hills. I changed the countershaft sprocket from the stock 14T to a 15T and also like this change for all gears. First gear is still usable for picking your way along slowly when you need to, and it will still pull sixth gear uphill. Fifth gear is actually nicer on the road and for hills because the engine doesn’t have to rev so much.
Other changes to complete the bike and make it fit include Precision luggage racks, Seat Concepts seat, lowered footpegs, skid plate, new handlebar and controls, and an Atlas throttle lock.