Motard Complete & Tested

As mentioned previously on this blog, this is a motard style conversion of a Honda CRM 250 using a 2007 model Aprilia RS-125 wheels, discs and front brake caliper.

A custom bracket was designed in Solidworks to adapt the radially mounted caliper to the original brake caliper mounting holes. Designing in 3D allowed the part to be simulated (FEA) with heavy braking loads and calculate the factor of safety, stress, strain and distortion.

One of the advantages of using the Aprilia wheels over the popular wire spoke wheels is that they incorporate a cush-drive to reduce driveline vibrations.

Testing found the brakes to be more than adequate. The bike was a lot quicker to turn into corners due to the increase in headset angle created by the switch from 21″/18″ wheels to 17″/17″ wheels. The bike also stood up out of corner leans much quicker too. If desired the characteristics could be toned down by making custom extended dog-bone suspension links to drop the rear of the bike and reduce the headset angle.

The biggest improvement was the cush-drive. This gave a slightly softer feel to the power delivery but really smoothed out the “snatchiness” felt when cruising or decelerating.

Overall a brilliant motard.


4 thoughts on “Motard Complete & Tested

  1. Hi guys,
    I don’t suppose you still have the solidworks file for the brake caliper bracket? If so, could I be cheeky and ask for a copy as I’d love to replicate this conversion on my own mk2 crm250.
    Kind regards.

    1. Sorry, having read the build write up properly I see that you have provided drawings for the caliper bracket, which will hopefully allow me to use the aprillia brakes and keep my current spoked supermoto wheels, albeit with a disc to suit.
      An amazing build and an even better write up. Great job, the bike looks great on the rs125 wheels!
      I think I’ll try to get the caliper sorted before considering the wheels as well.
      Kind regards, Benjamin.

      1. Hi Benjamin,

        Thanks for the kind comments and I have to agree that the CRM looks great with those wheels.
        Don’t forget to add the small reliefs that I mentioned in this post; Aluminium is a great material for a track bike but keep in mind that aluminium will fatigue, no matter how small the stress, so leave plenty of material, use fillets in the corners, make sure to de-bur and inspect often (as you would when owning a great bike like the CRM).
        I am missing having the CRM to ride around on but hope to get another bike project and do more development work on two-stroke engines in the future (even KTM have caught on to installing EFI on dirt bikes :).
        Will you be modifying the caliper or leaving it standard and bleeding it off the bike?

        Kind regards,

    2. Hi Benjamin,

      I do have the Solidworks and an .stl file of the part if you really want it. I recommend leaving a bit more material on the face where the caliper bolts to. I needed to add a 1-1.5mm spacing plate to get the right clearance for the caliper to the OD of the disc. And make sure you use high tensile bolts for mounting the bracket and caliper.


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