Thanks for all the help. Carb is brand new from 77. Jetted as directed on this site. But that doesn't mean a little tuning wouldn't help. When I say surging I mean that when I give it full throttle it will top out at 15 mph at most but occasionally will get a surge of 3 or 4 more mph and then back down to 15 mph. I've been thinking that the front plate is trying to close but rear pulley won't open and give enough extra belt. But I'll rule that out tomorrow.