Hello everyone.
This time I'm coming back to improving the front brake on my Honda XR250 BAJA (the Japan-market XR250 / MD30), which I looked into before.
In short, I'm leaning towards using a CRF250R master cylinder, and I found two problems with fitting it.
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XR250 Front Brake Feel: Smaller Master Cylinder or Kashima Pistons? (MD30)
The XR250 BAJA (MD30) front brake feels on or off. I compare two fixes: an 11 mm master cylinder (with a list of Honda donor models) or Kashima-coated pistons.
In the previous post, I was thinking about changing the front brake master cylinder bore from the current 1/2 inch (12.7 mm) to 11 mm.
After more digging, I found that some people have fitted the CRF250R master cylinder and brake lever to other bikes.
Most of the posts I saw were about fitting it to a Yamaha Serow.
So I got hold of a used CRF250R master cylinder. Even among CRF250R master cylinders, there seem to be differences by model year.
In the photo above, the CRF250R front brake master cylinder is on the left, and the standard XR BAJA master cylinder is on the right.
I photographed them from various angles to compare them.
Here, the difference in the size of the brake fluid reservoir stands out.
This is each master cylinder seen from the front. Again, you can see the CRF250R's reservoir is more compact.
This is the side view. As well as the smaller reservoir, you can see that the outlet to the brake hose is in a different position.
Next, I weighed them.
The CRF250R front brake master cylinder, including the lever, weighs about 276 g.
The XR BAJA front brake master cylinder, also including the lever, weighs about 360 g. The CRF250R's is about 23% lighter.
With the comparison done, I trial-fitted it to the bike.
From this angle, it looks fine.
Operating the brake lever with it fitted looks fine too.
But here the first problem showed up.
As the yellow arrow in the photo above shows, the CRF250R master cylinder can't sit right up against the kill switch.
The reason is the wiring coming out of the kill switch / starter switch.
Because of this wiring, I can't move the master cylinder any closer to the grip.
And the second problem:
The brake hose connection faces backwards, relative to the direction of travel.
With the brake hose I've been using, the hose twists and won't fit neatly.
I tried routing it round the back of the handlebar, even though I didn't think that was a good idea, but it doesn't look like it will fit that way either.
It looks as though I'd need a longer hose and a different banjo angle to fit it.
On top of that, I'd have to decide whether to use a hydraulic brake light switch or make an adapter for a mechanical switch, and think about the mirror holder too.