The "Montysan" XT225 conversion posts over on the Yahoo Big Wheel group don't have to0 terribly much detail, but he did post some photos. These are about 5 years old and it looks like Montysan has sold his BW and wandered off.
One of the photos shows what appears to be the left handle bar control switch from the XT225, so I conclude that he did use an XT225 harness. He definitely used the XT225 coil and CDI.
He decided to cut and bend the frame down tube to make the standard XT225 front mounting bracket work. I believe I would try to make a custom front motor mount that would work with the standard frame. That would be a piece others could replicate and would allow a future reverse conversion.
The photo album of Montysan's conversion are album number 102 on the Yahoo Big Wheel website. That's several pages down in the photo section. The resolution of the photos is not that high, but are adequate.
I have the same question. There are aftermarket upgrade bearing kits for the BW200. They are from Moose Racing, I think. If this is an exact bolt up, perhaps it would be a good time to drop in the new upgrade bearing kit. But, I'm not clear on whether I would need Tri-Z steering bearing, BW steering bearings, or whether they are identical.
Does one need a Tri-Z axel and spacers to make the Tri-z hub/disc work, or will the BW front axels and spacers do the trick?