My name is Kamil.
I have a problem with my Piaggio fly 125 2005, engine code m421- milage ~14k kilometers.
The engine starts and heat up perfectly, problem is with low power/low rpm, he can't hit more speed than 40km/h. On stand looks like everything goes right - engine hits low/middle rpm's slighly but not on the road.
What i done:
1. I cleaned carburettor (KEIHIN CVEK26), flow screw - turned twice from the close position. Also replaced vacuum valve to factory new (somebody can tell me how it work /should works?)
2. Changed to new one: fuel supply pipe, fuel valve low-pressure pipe, SAS pipe, air filter, spark plug - claerance 0.8mm
3. I set up claerance on valves in head : intake 0.10, outlet 0.15
4. I sealed air filter box with new bands - engine not respond for autostart spray.
5. Sometimes when I rev engine, it shoots in to exhaust system
6. I haven't looked yet under transmission cover - maybe here is a problem ?
Here is my video - maybe you'll catch something that I missed.