Piaggio XR 125, idles fine, revs up OK but under load it makes a sound and dies

hello everyone,

I am new to this community so if I post this on a wrong place I apologise.

So I have this 2002 Piaggio XR 125 cc 2 stroke that belongs to a friend of mine. I recently changed some old fuel lines etc and patched the broken plastic. Took it out for a ride, no problems, working like a clock...

When he was driving me back home (going up a slope), the bike suddenly makes a sound and dies. I am thinking our combo weight was too much for the old piston and it gave up. But no, restarting the bike, everything sounds OK, I let it idle for some mins, gently throttling up the bike is able to take itself up but past a certain point it makes this awful noise (like a spring is broken and gets caught up in the clutch) and the bike dies immediately. Going down the hill with 1 adult the bike runs...

Before I take apart things (because if something breaks during removal it is pretty difficult to get hold of spares due to the bike's age), any ideas? Anybody experienced the same thing?

 

Sounds like the clutch or belt. Should be obvious to see when you open the transmission cover

 

Thanks a lot for the reply. I opened the cover, the belt seems fine (no obvious wear or stripping). Guess I will need to crack open the clutch. Will keep you posted.