TW200 Forum banner

1 - 12 of 12 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter #1
Does anyone know of a big bore kit for the tw200 or will a xt350 or 250 bolt up or be chopped in?

I read there are 280 kits in europe but can't find anything on internet.

Serious replies only!
 

·
Registered
Joined
·
1,621 Posts
The mother of tw big bore links



http://www.google.co...lient=firefox-a



A fellow at adv went bigger but had mixed results (See Below)

http://www.advrider....ad.php?t=490048

You are going to have a hard time bumping the TW200 up very far. It is such a short stroke engine that even doing a 3mm overbore for an XT225 piston is only going to take it up 214cc. You are looking at a 5mm overbore of that little cylinder just get it up to 225cc. And remember, you are basically talking about a 125 engine that is already bored and stroked to go from 124cc to 196cc. So reliability may be an issue if you try to go much larger.



Back in the day I had my 200 overbored to accept an XS400 piston. That was a 2mm overbore (67mm to 69mm) and the mechanic figured we were about at the limit of what the liner would take with that. That 2mm bore took it from 196cc (same as the TW200) to 208cc. The XS400 piston has a higher compression shape so we had to make a pretty thick base gasket to get the compression down enough to run on premium pump gas.



After that it was a quite a headache to get it jetted right for the additional displacement, a Supertrapp muffler and opened up airbox. It was quite the little screamer when we got through with it. But it was a LOT of work getting the jetting dialed in. And we never did get it completely sorted out so it idled well. Ultimately it provided very little benefit over just adding a pipe, opening the airbox and rejetting a stock motor.



So, IMO, the bottomline from my experiment: I would leave well enough alone and just try to get the most you can from the stock motor. In fact, I still have that bike and plan to eventually put it back to stock if I can ever find the time to work on it. It was a much happier engine in stock form with the Supertrapp, airbox and jetting mods.



If I had wanted more than 200cc's I would have got a





2008 Yamaha WR250R







Price $5899 Dry weight 286 lb. Wheelbase 56.3 in. Seat height 36.0 in. Fuel mileage 51.7 mpg 0–60 mph 7.4 sec. 1/4-mile 15.47 sec. @ 81.90 mph Horsepower 25.2 hp @ 9200 rpm Torque 15.3 ft.-lb. @ 8200 rpm Top speed 85 mph
 

·
Registered
Joined
·
68 Posts
i dont know, but i have always wondered if a bw350 cylinder and head would bolt up... also i don't know the stroke of the 350, or if the wrist pin is the same size... i still play with the idea though, just need to do some more research.
 

·
Registered
Joined
·
1,621 Posts
I rode with a adv member last year in the mountains who had a xt250 & both our bikes were stock. He mopped the floor with me on the street. Any time he wanted by me is was no contest. I bested him when we hit really sloppy gravel roads. I just love having all my cargo space.
 

·
Banned
Joined
·
10,664 Posts
I had a thoroughly thrashed XT225 engine and about the absolute limit one could go to with bore and stroke was 310cc. Such an engine would not be dependable. Such an engine would require a custom piston, rings, rod, and liner, and machine work on the crank, case, cylinder, and head. Many $$$$$$$$. As far as cost effectiveness, I'd look at using a different bike and fitting the TW rims and tires.
 

·
Registered
Joined
·
3 Posts
The mother of tw big bore links



http://www.google.co...lient=firefox-a



A fellow at adv went bigger but had mixed results (See Below)

http://www.advrider....ad.php?t=490048

You are going to have a hard time bumping the TW200 up very far. It is such a short stroke engine that even doing a 3mm overbore for an XT225 piston is only going to take it up 214cc. You are looking at a 5mm overbore of that little cylinder just get it up to 225cc. And remember, you are basically talking about a 125 engine that is already bored and stroked to go from 124cc to 196cc. So reliability may be an issue if you try to go much larger.



Back in the day I had my 200 overbored to accept an XS400 piston. That was a 2mm overbore (67mm to 69mm) and the mechanic figured we were about at the limit of what the liner would take with that. That 2mm bore took it from 196cc (same as the TW200) to 208cc. The XS400 piston has a higher compression shape so we had to make a pretty thick base gasket to get the compression down enough to run on premium pump gas.



After that it was a quite a headache to get it jetted right for the additional displacement, a Supertrapp muffler and opened up airbox. It was quite the little screamer when we got through with it. But it was a LOT of work getting the jetting dialed in. And we never did get it completely sorted out so it idled well. Ultimately it provided very little benefit over just adding a pipe, opening the airbox and rejetting a stock motor.



So, IMO, the bottomline from my experiment: I would leave well enough alone and just try to get the most you can from the stock motor. In fact, I still have that bike and plan to eventually put it back to stock if I can ever find the time to work on it. It was a much happier engine in stock form with the Supertrapp, airbox and jetting mods.



If I had wanted more than 200cc's I would have got a





2008 Yamaha WR250R







Price $5899 Dry weight 286 lb. Wheelbase 56.3 in. Seat height 36.0 in. Fuel mileage 51.7 mpg 0–60 mph 7.4 sec. 1/4-mile 15.47 sec. @ 81.90 mph Horsepower 25.2 hp @ 9200 rpm Torque 15.3 ft.-lb. @ 8200 rpm Top speed 85 mph
Do you have a link to your build? Looks like you modded you T-Dub pretty good.
 

·
Banned
Joined
·
10,664 Posts
xr100.com took the TT-R out to 250cc, and that's pushing it. That requires a TT-R or XT crank and a resleeved cylinder.
 

·
Registered
Joined
·
129 Posts
About 40 years ago I had a Yamaha 125 cc Enduro (electric start like the TW) that I wanted to get more torque out of. Asked the mechanic if I could put a 175 cc cylinder and piston on it keeping the small carb. (rejetted) for torque. His answer: "Nope, different cc's onto it!". Never did figure that one out.
 
1 - 12 of 12 Posts
Top