Wednesday, March 16, 2016

Honda CRF250L Supermoto using CBR250R/CBR300R Wheels

New topic entitled "CBR250R/CBR300R wheels on CRF250L/M"

in Thumpertalk forum "CRF250 L/M

Supermoto Conversion Introduction:

Disclaimer: All these modifications you take at your own risk. I am not liable for injury or loss due to this modification. No responsibility or liability is accepted for any other information presented in this post.

So I said I would start a build thread for the Supermoto guys that were asking about the possibility of running CBR wheels on our CRF250L/M, but this is an open thread for anyone that is curious...
It all started out around last year when a member on the Facebook CRF250L Owners Club asked if it was at all possible. One our members on the Facebook group, Pete decided to tackle the mod and do a very short write-up. However, when I decided to tackle the build to run cbr wheels I drug the build out over several months and just now got it "finished".
If you are overseas and have access to the CBR250RR their wheels are different than the CBR250R and won't require the same kind of modifications.
I currently don't have access to my photos of the build so I'll post the actual build, when I get home later tonight. But I'll start everyone out with basic information and parts list.

Basic Honda Parts Comparison (stock numbers):


  • Front Wheel : 21" x 1.60
  • Front Tire: 3.00-21
  • Rear Wheel: 18" x 2.15
  • Rear Tire: 120/80-18
  • Sprockets: 14/40


  • Front Wheel: 17" x 2.75
  • Front Tire: 110/70-17
  • Rear Wheel: 17" x 3.50
  • Rear Tire: 130/70-17
  • Sprockets: 14/39

CBR250R (CBR300R)

  • Front Wheel: 17" x 2.75
  • Front Tire: 110/70-17
  • Rear Wheel: 17" x 4.00
  • Rear Tire: 140/70-17
  • Sprockets: 14/38 (14/36)

Part List:

  • CBR250R/CBR300R Front and Rear Wheels
  • CBR250R/CBR300R Front and Rear Brake Disc
  • CBR250R/CBR300R Rear Cush Drive/Hub Assembly (if not included with wheel)
  • CBR250R/CBR300R Rear Sprocket (stock or aftermarket)
  • CBR250R/CBR300R Rear and Front Spacers (both sides)
  • CRF250M Front Caliper Bracket (45190-KZZ-A21 or https://bikerzbits.c...90-kzz-a21.html)
  • Front and Rear Tires (I personally opted for the CRF250M sizes)
  • Countersunk Bolts (M8 x 1.25mm)

Tool List:

  • Angle Grinder/Hacksaw/Dremel
  • Bubble Level/Straight-Edge
  • Sandpaper
I didn't have a Angle Grinder so I made rough cuts with a hacksaw and them smoothed the cuts out with the dremel tool.

Thoughts on Gearing:(
On the CRF250L when you change just the tire size from the CRF250L size to the CRF250M size, the gearing is about 5.8% lower (like running a larger rear sprocket).
However, the difference between the 250L and the 250M with tire size and sprockets is about 3.1% lower.
My first test run of my CBR250R wheels were with the CBR250R gearing setup 14/38. With the smaller wheel/tire and the small rear sprocket the gearing is about 0.5% lower.
The difference in the test run set-up isn't noticeable at all. Also, you run into the problem of chain adjustment. On the stock OE chain, the 14/38 set-up is adjusted way back in the red zone to get proper chain slack. To keep the use of the factory chain I'm personally opting for a 14/40 setup on both dirt and street (I may go to a 14/42 for dirt later, still allowing me to use the OE chain size).

I ordered a steel CBR250R 40T sprocket (Vortex). You can find 38T and 40T in steel, anything else you have to find in aluminum or have someone custom make it for you.
I won't have the sprocket changed until this weekend because I'm waiting on parts and I need to install my SpeedoDRD. All 6 of the sprocket bolts/nuts on the cbr250r wheels were seized so they had to be cut off/drilled out. Sprocket bolts and nuts come in tomorrow.