Thanks for all your replies!
@zombie
I really don't know why Tehnigas exhausts are not sold here (I live in Croatia), but I did see that they have official importers in a few neighboring countries.
Before logging into this forum I never even heard of Tehnigas, but then again, this is my first scoot, and I didn't pay attention to these things before.
Now back to the problem.
Luckily I wasn't to eager to get my exhaust chopped open, because the sound is almost normal again
One very important thing I didn't mention when I started this thread is that the day before the sound started to change I had my tires changed.
The stock Cheng Shin should be called Cheng Sh*t, they are just terrible, and after a few dangerous situations in the rain I decided to get a decent set of tires.
To change the rear tire the muffler has to be taken off, and maybe when the muffler was put back on the exhaust gasket (or muffler packing collar as described in the service manual) it didn't fit the way it should.
The service manual says that a new gasket should be put on every time the exhaust is taken off, but I didn't have a new one, so the old one was reused.
Now after about 150 km since the beginning of the problem, and a few longer trips out of the city at full speed, the sound is almost back to normal.
The service manual states that the cause of exhaust noise could also be:
- Faulty air injection cut-off valve
- Broken vacuum tube
- Faulty reed valve
I'll get these checked by a scooter mechanic to see the above mentioned parts are ok.
