Sorry , should have put in more info. So it was originally a'78 2 speed maxi mkII, but the 2speed transmission was hosed, so I switched in a whole new 1speed transmission and aftermarket 50cc topend, kept my old stator and flywheel to make the wiring easier.
The tank is sparkling, I spent a week degreasing, derusting, and por-15ing the bastard so gas flows crystal clear. The carb is rebuilit 14mm bing with all new gaskets, needle, jet, float, etc... Clutch is good, new points and condensor. Far as I know this thing should work. The topend is a 50cc aftermarket kit , and I do have a techno boss pipe, but i kept on the old exhaust and #54 jet that ran with the 2hp 2speed engine. I realize I need to tweak and rejet since it's now a 1speed engine (but with the kit and the high torque head, still 2hp?) but still doesn't explain why my lowend pull is so pathetic, even after switching the front sprocket from 18T to 14T. I guess I could put it back but I don't think that's the problem and would probably only make it worse.
Again, when i did slap on the techno boss and up jetted to #60, i could move up to 20mph, but take off still required pedaling, but with the stock airbox and pipe this thing can't get up to 5mph and bogs down at full throttle.
Even if it were jetting issues I still can't see it explaining why I can't get this thing to pull me off the line itself withough pedal help, I'm a big guy (200+) but I shouldn't be able to bog the engine by pressing down on the seat with one hand.