I've finally got my moped running. It's a 1977 Negrini Harvard with a Morini MO-2. This was a junkyard bike in really bad shape. The piston and cylinder were trashed so I found another motor with a good piston and cylinder. I have a Dellorto SHA 12 carb, and I've installed new rings.
It starts easily and runs but it produces a lot of smoke. When I take it on the road, it tops out around 5 mph.
How should I start troubleshooting?
If I installed the piston wrong would the engine behave this way?