Grand Dink 250/Grandvista 250 engine noise (Solved)

[Rudolf]

I've bought a second hand Kymco Grand Dink 250, made in 2003 with 27033 km's on board. It ran in Italy. The clinking noise from the engine is only at idle, but it seems to dissapear at higher RPM. I've tried running the engine without the CVT because i thought the noise is coming from the variator. Could anyone explain me what is the problem and what makes that noise?
Here is a clip with my bike:
Kymco Grand Dink 250
Another clip showing the engine running with the variator removed:
Kymco Grand Dink/Grand Vista 250 engine noise

[Rudolf]

I've found out after dismantling the engine that the timing chain was over stretched, it had 0.5mm of free play on the length of each link. The chain tensioner couldn't tension the chain properly so the chain flapped around inside and hitting the walls of the crank case at low RPM. The crankshaft is OK. Also the starter system is OK.

[Rudolf]

Finally I've finished the repair on my scooter. Now the bike sounds a lot better than before, now that I have a new timing chain and a new piston. I had to take my cylinder to be honed smooth to eliminate the scratches. The chain and piston are GENUINE KYMCO parts.  Motorul meu Kymco Grand Dink 250 după reparare - My Kymco Grand Dink 250 after service