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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 April. 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 install tips and 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.
Kit is quality with everything needed. Have 500 miles and running strong. This kit doesn't turn the engine into a huge powerhouse, but does give it a nice boost while being very managed. Would do it again if ever buy another CRF300L Rally.
All the parts seem to be very well constructed and the tolerances are precise. The stock Honda parts are very nice and necessary to give the CRF300l the motorcycle it was really meant to be without compromising reliability and longevity. An excellent purchase for a superb uprade!
My path to owning a CRF300L isn’t an obvious one, coming from a sports bike background, a track day enthusiast and a speed freak, my first move towards a dual sport bike was a 2019 CRF250L. I had an R1 at the time as well as the little 250.
The 250 was stock when I got it, over the next few months, I added a K&N filter, velocity stack, FMF pipe and a CBR250R ECU. It transformed the bike and I loved it. I found that I was using the 250 most weekends and my R1 was basically a very pretty ornament.
In 2022, I sold the 250 and the R1 and bought a new £300L, first impressions weren’t great, it was slower than my 250, so I started to look into upgrades. I was able to get a high flow filter, fake FMF and a CBR300R intake boot but struggled to find anyone who could remap the ECU.
550 Performance were not doing the EU ECU at the time but I did find a company in Italy called Piasini Engineering, I sent off my ECU for a stage 1 tune and it improved the 300 quite a bit, but I wanted more.
Christian, the owner of Piasini had told me that he was working with Maverick at 550, so after a few months of riding the stage 1 tuned bike, I contacted Maverick and arranged to have a 1.5 tune and also add the CBR300R cams. This made the more responsive throughout her range and the bike was so much more fun to ride.
I then started seeing YouTube videos of the Ari Henning big bore kit, and it immediately had my attention. I watched these videos over and over again before finally contacting Ari to build a relationship before purchasing.
It’s a big thing to mess with a bike that you love, so you need to make sure the parts you are adding are reliable and the customer service has to be brilliant too.
I found Ari to be incredibly helpful, always willing to offer advice and also explained the history of the big bore kit, proving its durability over time. This gave me the confidence to go-ahead and buy the BBK, as well as asking Maverick to upgrade my ECU to a stage 3 tune. I must add that during this process, Maverick has been extremely helpful too.
I’ve had the BBK on the bike for 250 miles, it lives up to hype and then some, it transforms the bike into the bike of my dreams, it has so much more power than stock, everywhere. Every time I ride it, it makes me laugh out loud as it just wants to rip, wherever it goes.
I’m mostly a road rider and love twisty countryside roads, this bike is perfect for this, the increased torque makes it the perfect weapon for powering out of long sweeping bends or chucking it into tight corners and racing out with the front wheel skipping on the tarmac.
The performance increase is right across the range, what has surprised me is the increase in top speed though. My gearing is 13/42 so previously I would top out at 80 (GPS) but now it flies past 80 and will hit 92, I’m pretty confident that with standard gearing it would get easily the over 95 and may even touch 3 figures.
Finally, if you’re thinking of doing this, don’t do what I did and do it in 3 stages, go straight for the BBK and stage 3, you won’t regret it.
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.
Kit is quality with everything needed. Have 500 miles and running strong. This kit doesn't turn the engine into a huge powerhouse, but does give it a nice boost while being very managed. Would do it again if ever buy another CRF300L Rally.
All the parts seem to be very well constructed and the tolerances are precise. The stock Honda parts are very nice and necessary to give the CRF300l the motorcycle it was really meant to be without compromising reliability and longevity. An excellent purchase for a superb uprade!
My path to owning a CRF300L isn’t an obvious one, coming from a sports bike background, a track day enthusiast and a speed freak, my first move towards a dual sport bike was a 2019 CRF250L. I had an R1 at the time as well as the little 250.
The 250 was stock when I got it, over the next few months, I added a K&N filter, velocity stack, FMF pipe and a CBR250R ECU. It transformed the bike and I loved it. I found that I was using the 250 most weekends and my R1 was basically a very pretty ornament.
In 2022, I sold the 250 and the R1 and bought a new £300L, first impressions weren’t great, it was slower than my 250, so I started to look into upgrades. I was able to get a high flow filter, fake FMF and a CBR300R intake boot but struggled to find anyone who could remap the ECU.
550 Performance were not doing the EU ECU at the time but I did find a company in Italy called Piasini Engineering, I sent off my ECU for a stage 1 tune and it improved the 300 quite a bit, but I wanted more.
Christian, the owner of Piasini had told me that he was working with Maverick at 550, so after a few months of riding the stage 1 tuned bike, I contacted Maverick and arranged to have a 1.5 tune and also add the CBR300R cams. This made the more responsive throughout her range and the bike was so much more fun to ride.
I then started seeing YouTube videos of the Ari Henning big bore kit, and it immediately had my attention. I watched these videos over and over again before finally contacting Ari to build a relationship before purchasing.
It’s a big thing to mess with a bike that you love, so you need to make sure the parts you are adding are reliable and the customer service has to be brilliant too.
I found Ari to be incredibly helpful, always willing to offer advice and also explained the history of the big bore kit, proving its durability over time. This gave me the confidence to go-ahead and buy the BBK, as well as asking Maverick to upgrade my ECU to a stage 3 tune. I must add that during this process, Maverick has been extremely helpful too.
I’ve had the BBK on the bike for 250 miles, it lives up to hype and then some, it transforms the bike into the bike of my dreams, it has so much more power than stock, everywhere. Every time I ride it, it makes me laugh out loud as it just wants to rip, wherever it goes.
I’m mostly a road rider and love twisty countryside roads, this bike is perfect for this, the increased torque makes it the perfect weapon for powering out of long sweeping bends or chucking it into tight corners and racing out with the front wheel skipping on the tarmac.
The performance increase is right across the range, what has surprised me is the increase in top speed though. My gearing is 13/42 so previously I would top out at 80 (GPS) but now it flies past 80 and will hit 92, I’m pretty confident that with standard gearing it would get easily the over 95 and may even touch 3 figures.
Finally, if you’re thinking of doing this, don’t do what I did and do it in 3 stages, go straight for the BBK and stage 3, you won’t regret it.
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.