i just got a 78 puch maxi luxe 2 hp. it has sweet pick up, never threatens to just shut down, rides smooth, and feel great. no complaints except for that it seems to top out at 20 mph on a smooth flat road. i have a pretty bad fuel mix in it right now but i wonder if that would make it run so slowly. the carb is clean, the petcock will need to be replaced in due time but it's doing the job fine. would it have anything to do with the exhaust? do 2 hps just run slower? thanks!