Puting BIG tires on an XR400

[Bultaco206]

You ever get over never winning a title?

??

[TWrider]

Its a serious question, I know it would require a good amount of fabrication and im not afraid of that, I was just looking for suggestions on ways to do it.

Yes, It can be done, In fact I'm presently working on a similar project.

In my opinion jackshafts suck (so do kickstart only, and liquid cooling, when it comes to fat tire fun bikes for use in tight woods trails and creekbed exploring). So I am using the Yamaha TW wheel setup. I've decided on using the SRX250 engine, planted in a highly modified xt350 frame. I want to use the XT frame because it's street legal already and has a low seat height. The SRX has the electric start that the XT350 engine lacks. It also has a split drive shaft cover that the XT lacks. The split cover is important, as I'm having a shaft extension made to move the chain throw outboard in order to clear the big TW rear tire. The extension will ride in a modified drive shaft cover/bearing carrier. The frame down tubes will be cut and will make a 1" jog on each side in order to make room for the TW swingarm. In addition the seat stays will have to be cut and modified to meet up with the new widened downtubes.

On the right side of the bike, a piece of the old TW seat stay will have to inserted to allow for the extra 1-2" to the right that the muffler will have moved in order to clear the big TW tire.

The SRX250 engine is a true DOHC air cooler like the TTR250, is rated at 28hp which is about 12 more than a stock TW200, and will improve freeway cruising considerably. The extra 6th gear won't hurt either. It has a bolt pattern that will fit the XT frame with minor mods. Many of the engine parts can be interchanged with the xt/tt350, It can also be potentially be taken to 350cc and beyond as the barrel is nowhere near close to the headbolts.

Now of course It won't be an xr400/TW/BW mongrel, but these types of modifications should only be undertaken on real bikes that come from manufacturers that don't build cars.

Joking aside, expect to run into the same sorts of problems should you wish perform the modifications to the single cammed, 5 speed, XR.

If I had the money I'd rather do this mod to a TTr250, but I already have all these parts sitting around. The TTr also has a higher seat height, and may have problems getting it registered street legal. ?