Can anybody please give me some advice. I've recently bought a 150 NSR 1997 model. It goes well, however the engine is extremely noisy. I've already had the piston replaced and some work done on the clutch. This lessened the noise marginally. The local machanic who worked on the bike said that the "valve" is working properly and that the noise is typical of 2 stroke bikes - although I have heard other 2 stoke bikes (same model) purring like kittens. The noise generally sounds very "tinny" and sometimes it actually disappears (but only for a few seconds). This is my first 2 stroke bike and whilst I know that 2 stroke engines are somewhat noisier than 4 stroke, I think mine is just tooooo bad! I'd really appreciate some advice and/or comments... thanks guys