Hello! There are many places of upgrade 125 cm3:

http://www.unlimited-power.net/

http://www.bihr-racing.com/

I buy my upgrade kit in bihr-racing, but now, I don't know why, they don't have it.

Good luck!

Hello every body!

If you remember, I did the modifications of the cilynder of Birth-Racing. I have finished the work. At the end, I use a 16 point of pinion with 51 point of "courone". I use the same box of air filter, with a the flex piece of TW200, and I use a Keihyn 30 carburateur. The results are lose a little bit of very low revolution power, but win more power in high revolutions. I before change the tires and I use the original tyres Brigstone of yamaha TW 125 type II, and the speed counter reduce the speed 5 km/h. Before in 125 cm3 with the new tyres, the top speed was 95 km/h, and now the top speed is 118 km/h. The speed cruising is 100-105 km/h, and the top speed in 4th gear is 95 km/h. The fuel consumation is the same than before: 4.58 liters for a 100 km in a mix city-road use!. And no oil consumation. I'm very happy  :-P  :-P

Hello another time!
Sorry about my english!!!
 I have news of the modification of my TW 125... Sorry, now is a TW 165. :-D  :-D . We make modifications also in "culasse", making bigger the admissions and exhaust, changing valves for news. For the moment I use the same carburator. I have done 70 km only, and the feeling is have more acceleration and power in low revolutions(in high I don't know. It's too much new!!). For an example, when I went in a mountain road, before I went with the 3 and 4 gear medium-full gas. Now I can go with 4 and 5 gear with 1/3 of gas. Now the acceleration comes in  a very low revolutions of motor, and it's more nervious (When I open a little of gas, goes up revolutions inmediatly). Another very different thing its the brake of the engine: when I cut the gas, the bike decrease the speed immediatly, similar when I went in the 3er gear in 125. In a few days I will go to the mechanic to correct carburation and change pinion(two point bigger) to increase speed.

I wish don't break the motor for a long time.
If you need some information, in my bad english I try to answer.

I'm sorry, I don't have pictures of modifications.

Salut! Adeu!

Hello! I'm sorry but I don't speak French. I come from Mallorca and I speak spanish or catalan, and a little bit of english. Your web is very interesting, also in spain we don't have a website for the TW. I have a TW 125 type I, and I will upgrade to 175cm3. I buy this kit in www.bihr-racing.com. In this web, they offer the Wisseco(165cm3) and Wossner(140cm3) kit, and I decide for the Wisseco. But in the end, Bihr-racing, send to me a 175cm3 Wossner kit. I read a lot in your forum about the differents preparations, and seems the IP preparation. My mechanic is specialist in upgrade Harley Davidson, and he says that if the work is well done, I won't have problems(oil consumation!!). In 15th of January I will begin the work!! If somebody is interested, I will inform about the result.

Adeu! (Au revoir!)