Help! My name is Peter. I live in the Chicagoland area. In 1978 I bought a new Garelli Grand Sport (on chain guard Rally Sport) 50cc engine #F285120. I used it for about two years. Put on about 900 miles. I think near the end of the two year period my son put in some of the wrong type of motor oil then proceeded to try to fix it. It would start fine but after about 10 minutes it would stop running. It was stored from then 1980 until a few weeks ago.
I cleaned it up put in a head gasket. Cleaned up the carburetor and put in new gas. It started up and ran fine. Then the problem. It runs for half a hour and longer but then it loses power and in some cases it stutters and some times locks up. I can usually start it again but it does not have much power. If I let it cool overnight its starts well and runs well. Don’t know were to start. Any help would be appreciated. I have a complete and well written manual (Owner Service / Repair 1976-1978)that came with the Moped. By the way if anyone needs parts of the manual please let me know. — Thanks — Pete Kiefert — kiefertp at uti.com