I would lean toward fuel. Sounds like maby running real rich (choke out?) and fouled plugs. Was it smoking from both sides? 20 mins. to start, sounds about like the right time for flooded engine to recover. That's the best I got. Hope you made it home OK. Good luck, and don't forget to check the simple stuff first.
- Come to terms with the ass that bears you/ 07 CB250/ 07 1100 Spirit with Velorex sidecar