BBR Big Bore Kits

Company: BBR Motorsports

Price: $329-$399

  • The bang for the buck in power is pretty substantail.
  • Does not decrease reliability.
  • Makes the bike easier to ride with improved power that you can really use.
  • Compared to the price of the bike, the mod can seem expensive.
  • You need decent mechanical skills to install.


  • Writer: Jimmy Lewis
  • Photographer: Jimmy Lewis

What it is

BBR Motorsports (Brown Brothers’ Racing) has been designing and producing quality, high-performance products for off-road play bikes since 1996. They are one of the most successful companies and one of the few to survive the multiple booms and recessions of minibike modification madness. Today they produce a wealth of products to make your kid’s (or your) play bike faster, stronger, and way more badass, as much as your pocketbook will allow. 

The Yamaha TT-R 150 Big Bore Kit with Cam is what we are specifically showing in the photos in this report but we have used many of the various kits from 50cc to 150cc. There is a similar kit for the Honda CRF/XR 100 that we have a lot of time with as well and feel the same about in performance.

This complete kit requires no exchange and comes with a custom-made aluminum cylinder with a steel liner with the BBR logo. It comes with a 58mm piston, ring set, piston pin & clips, and gasket kit including cylinder head and base gaskets. Additionally, a high-performance BBR MX Grind camshaft is added for even more power. The Yamaha kit has instructions and takes the stock 124cc displacement to 144cc. The Honda kit goes from 99cc to 118cc. The cost is $399.95 and the Honda kit is $329.95.

Check for more info.

"BBR produces products to make your kid’s play bike faster, stronger, and way more badass--as much as your pocketbook will allow"

How it works


There is no replacement for displacement and nowhere is that more evident than in smaller displacement engines. With decades of riding and racing Honda CRF/XR 100s and Yamaha TT-R125s we know this and we know how to get a quick cheat in on our buddies. Years of sourcing and configuring different pistons and sleeves to shove in our cylinders as well as finding the magical niche company manufacturing these parts is over. BBR did the homework and put the parts you need in a box. 

Installation is as simple as installing a standard piston and cam so if you are capable of this the job is easy. The instructions walk you through the process and point out some little helpful tips along the way with the Yamaha install being a little tougher than the Honda from our experience. You have to let the engine hang down in the chassis to get the cylinder head off where on the Honda you do not.

We have, over the years, put 100s of hours on these kits and can say it is the best bang for the buck you can get if you are searching for a little more power. And a significant amount of torque which is what you really want, especially at lower RPMs. On either Yamaha or Honda the increased roll-on power and decreased stalling make the bikes way easier for novice riders to ride and way more fun for experienced riders. We’d estimate that with just the big bore kits, running standard exhaust systems, you are getting a 20-25% increase in power which is pretty substantial. The cams in both kits let the bikes rev further which boosts peak horsepower even more. This was particularly noticeable on the Honda kit. BBR’s jetting guide comes in handy and is spot on.

With the increased power we never experienced any durability issues with them. In fact, we ride the wheels off of these bikes on trails, backyard tracks, and even floating valves on a flat track. We think the pistons will last as long as stock and for these bikes that mean 100s of hours. 

So if you have a Yamaha TT-R 125 or Honda CRF 100 this is the safe, easy and simple way to get a little more gusto for you or your kids. And since they look like standard parts from the outside, if you are pulling up to the starting line, no one will know!


"Running standard exhaust systems, you are getting a 20-25% increase in power which is pretty substantial"

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