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.

In my search for the perfect unicorn ADV bike, I initially reached out to Ari to pick his brain about the 301cc conversion process. While I was still deciding on the right CRF L Rally model, I wanted to get some expert advice. I’m fairly mechanically inclined, but I knew if I were to get a 250L, that splitting the case to replace the crankshaft wasn’t something I wanted to take on for the first time—especially on a bike I needed to be Honda-reliable for off-road adventures.

After discussing my options, I landed a 2018 CRF250L Rally for a decent price. Excited about the build ahead, I pulled the motor and dropped it off along with the throttle body for Ari to work his magic. Throughout the process, the communication was top-notch, and I welcomed his transparency.

An unexpected issue was discovered with one of the cam seats being galled due to a lack of lubrication, so the head had to be replaced. Ari installed the crankshaft, his complete 301 kit, fab'd a spacer to swap in the proper injector for the throttle body, and even modified a velocity stack to fit the specific build. The quality of work was exceptional, as you’d expect from someone with his repertoire in the motorcycle industry.

While the CRF300L Rally offers a lot of upgrades over the CRF250L—such as a lighter frame and larger fuel capacity—if you can find a good deal on a CRF250L and have some budget left for the BBK, I believe this kit really levels the playing field!

Since completing the build, I've added a 1.5ga "camel" style fuel tank, upgraded the suspension front and rear, and made other adjustments to tailor the bike to my needs. I’m currently in the process of breaking in the bike, and all I can say is WOW. Big thanks to Ari and Maverick at 550performance.com for laying the groundwork to make this project possible.

P.S. if anyone was wondering, my initial MPG measured in the high 60's with mixed freeway and dirt riding.

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.

I contacted Ari with questions many times about his big bore kit. I didn't yet own a 300L, but was considering one.

At one point, he mentioned that he had a low mileage, well setup bike coming into the shop and was I interested? Absolutely!

What came out of his shop is nothing short of a BDR unicorn. It could use a touch more power for pulling hills and into headwinds, but this bike is perfect for ADV travel. It's quick and handles very well. It'll plod along desert trails, and rail through the sand, then hop on pavement and get you where you need to go. Ari says his mods don't affect reliability, so I'm hoping for many happy, dirty miles

Part of the build was adjusting the existing Race tech forks and Cogent shock to my needs and it's perfect. This bike absorbs 25# of full travel/camping luggage and floats over woops in the desert like a magic carpet .
Throughout the process, Ari impressed me with his quick replies and respectful dialog. He's a pro through and through and a genuinely nice person that has this platform figured out. He asked to reach out anytime with questions or any help. I believe he'll be there if needed.

I love supporting one man shows doing cool shit. He epitomizes this. Buy with confidence!

So having a few street bikes and an adventure bike, I wanted something more dirt oriented, and something that you could ride on single track. I grew up in the 2-stroke era of dirt bikes, but wanted something more street worthy, and probably a little mellower, so I got the 300l rally. Loved it and just acknowledged some of its shortcomings, one of which was power. I put a thousand miles on it with minimal upgrades and wished it had just a little more power for some hills and rougher terrain, as well as some top end power for the little bit of highway riding I do on it. The big bore kit along with cans and air mods have made what I thought would have been impossible amount of difference for that little motor.

If you’re on the fence like I was, do it. It took a weekend to put in, with basic mechanical skills and having never taken a 300l apart.

I decided to turn my little Honda into an adventure bike capable of tackling any challenge. After upgrading the suspension, the handling improved significantly, but it was still lacking power. While watching YouTube, I came across several channels featuring Big Bore kit upgrades.

I decided to go for a full upgrade, including CBR camshafts, an Airbox mod, a 550 Performance ECU, and the Big Bore kit – and I have absolutely no regrets! The little Honda transformed into a completely different bike: faster, stronger, and more agile.

I highly recommend this upgrade to anyone looking for more power and torque. Special thanks to Ari for his advice and support – none of this would have been possible without him.

After my stock motor locked up on the highway I already new I wanted to go with a CBR300r crank and intake cam. I had also been eyeing Ari's 301 piston to go along with it. After seeing the long track record of reliability and seeing JaketheGardenSnakes videos I knew I was in good hands.

I did not have Ari build my engine since I prefer to learn these things myself, he did however give me tons on help through text. His knowledge of these engines is tip tier and his response time was great.

I, sadly, was one of the very few that had issues with my build though. I believe we narrowed my issues down to improper break-in and using subpar GN-4 oil. The second one I tried to save some money and had a local shop do my cylinder which we later realized was not honed properly and the piston was mishandled resulting in oil consumption and weird surging. Lessons learned.

Even with all this Ari continued to work with me selling me one of his race spares. Since then my bike has been solid. I have not been easy on it either. It has multiple track days and many highway miles on it.

I will also add that I was in contact with maverick of 550performance at the same time and he was also a great help with the build.

I am thankful that we have these amazing people in the motorcycling community and especially ones that love these cheap little bikes like the rest of us.

I had Ari build me an entire motor for my CRF300l. We spoke on the phone to figure out the build spec and he kept me updated as the head got ported and the bottom end went together. Then he shipped it across the country to me and I couldn't be more pleased with the power. It's everything I was looking for in this build. He was a true professional from start to finish, and I would highly recommend him for any mechanical upgrades for anyone looking to improve there bike's performance!

Almost 1k miles on this kit now and I am still blown away with the transformation every time I ride it. This kit completely transformed the bike into a different machine. I did the full stage 4 build with cams, intake, tune, etc and it pulls like a freight train through the full rpm range in every gear. It’ll now rev out to redline in 6th gear no problem. It absolutely rips on the trails and on the road. If you’re on the fence just do it you won’t regret it, I wish I did mine sooner!

Having bought the Honda CFR L Rally strictly for the street, my first opinion was great bike, handles well , super light and fun to ride. The problem was it felt under-powered. I researched the Web and came across Ari Henning’s fix. After talking to Ari, we decided the Big Bore kit, Airbox mod and CBR Cams would transform this little guy into what I was looking for. Couldn’t have been happier with the results and the professionalism of Ari. He did all the work (we live in the same area) he told me how much it would be and delivered what he promised. The bike is really much more fun to ride now and the parts transformed my little Honda into a kinda scary bike. 90 MPH on the freeway, on a little dirt bike is exhilarating!

After riding big ADV bikes for a few years I opted to build a small ADV bike for BDR type rides and went with an Ari Henning big bore kit. Every time I ride it I chuckle at how FRIENDLY and EASY to ride the bike is. I have put 3500 miles on the big bore kit tackling NM, UT and CO BDRs, which includes technical riding like Lockhart Basin in Moab and Black Bear Pass in Colorado. Most of my riding has been above 8,000 feet (and as high as 12,000!) which saps a bike’s power, but the 301 works great. I see this bike being in my fleet for years to come. Kudos to Ari for finding the right recipe on this one!

Since it was released I have been developing my CRF300 Rally into the ultimate light weight adventure bike and documenting it on my YouTube Channel: Shonky Productions https://www.youtube.com/@ShonkyProductions.

It has taken me on many great adventures throughout Australia but I always wished it had a little more horsepower and a little more torque for both off road work and highway performance. When I heard that Ari had developed a big bore kit for the CRF300, with his years of experience racing the CBR300 (same motor), I was confident it would be reliable and wasted no time ordering a kit.

The kit came with everything needed for the conversion and I was very impressed with the quality of the components. After installing the kit and a matching tune from 550 Performance I was immediately impressed. Not only had my prayers for more power and torque been answered but the smoothness of the motor had not been altered, an issue on some big bore kits with oversized pistons.

The bike was now more responsive and fun to ride with the added bonus of being able to pull taller gearing, thanks to its increased torque. The taller gearing lowered my revs on the highway while still having power to overtake and made the bike a much nicer “Adventure bike”.

I have been running the 301cc big bore kit for a year now and have put over 10,000km of abuse on it without any issues. In my view this is the best modification to increase power and torque, and I have tried them all. Check out my videos on the 301cc kit and see for yourself. It’s a big thumbs up from me.

Sean

https://youtu.be/7z-LOx6IcfY?si=V4s28FP8UyVYylWY

I had the privilege of working with Ari Henning, a record-holding racer with tens of thousands of miles under his belt as a testament to his expertise and reliability. Not only did he sell me the big bore kit, but he also installed it, complete with a CNC ported head, upgraded cams, air box modification, and professional tuning. The results are exceptional. The engine delivers significantly more power across the board, with a noticeable improvement both at low RPMs and as the revs climb. Ari’s extensive experience, particularly with this series of Honda motors, is evident in the quality of his work. His knowledge and craftsmanship make this investment well worth it. If you're considering a bulletproof build, don't hesitate—Ari's proven expertise ensures outstanding results.

Excellent products

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.