I am trying to find out what larger displacement engine will fit the '89 TW200 without chopping it up too much. Thank you ahead of time for the insight. I hav been combing the old threads but cannot find much on this subject.
Wouldn't it be easier to get a bike with the engine you would like, change out the swing arm and put a fat tire on. Would most likely be a pain as it would have to offset somewhat to adjust for sprocket and chain clearance. Just saying. modification can be a b.
tw was my first bike, after about 6 months I was looking for more power. got an old klr650 for under $1000 (a xr650 or dr650 would have been fine too) I am perfectly happy with the tw/klr duo. a klr is not a speed demon, but compared to the tw it feels like a wild horse, and I can keep up on the interstate and when you get off the 650 you'll appreciate even more how darn easy and fun the tw is to ride. that said---put a ktm 250 2stroke in there!!
The various options for the countershaft were discussed at length on a thread on another forum (I can't seem to find it again), and included making a shaft extension with internal boached splines (considered the best idea, but VERY expensive), havind a whole new shaft made (also very expensive, and al kinds of heat-treat/hardening issues), and some other stuff, which I can't remember.
I really think the best approach is using the TW countershaft in an XT250, and providing oiling either internally, or through an external oil line/drain. But until someone has both bikes (or engines) side-by-side, all this is barely informed guessing.
The main problem I have with the swap route is that all the Yamaha motors that are the best candidates are rare birds. Power to weight , still keeping it streetable, electric start, air cooled, keeping frame geometry, are all factors, In my opinion the absolute best swap would be the TTR 250 engine. In the states, these are rare engines. Yamaha was insane not to offer a TW 250
or XT with that motor, they finally discontinued the TTR250 for the US because they weren't selling enough, go figure? What do they expect if they don't make a street legal version available? The TTR 250 is something like 28-30 HP stock, an instant 10 hp increase for only an extra 20 pounds weight penalty, It's physical dimensions and power are similar to the old XT 350 engine, but with electric start up under the carb. I'm pretty sure US buyers would plunk down an extra $1000- $1500 for a larger, more powerful TW.