That's right...I'm crazy enough to tune a Columbia. Suspension stinks. Clutch is suspect. But so far I have a Quich pipe and a Dellorto 15.15 on it and I can get 30mph. That's with the junk 49cc tapered jug. Up from about 25 if I didn't eat that day.
So here's my goal: ride it to work. Then maybe I'll sell it.
So. Who has some nice jugs for me? And if you're going to offer me a used part that's no more than 10% less than new, don't bother offering. I'm from the old school when ebay and used parts on the interwebs were an actual bargain. I'd buy new before used if I'm only saving a few bucks.
What I'd consider:
505C/D (square jug)
Just about any kit that'll fit and run well without porting
Maybe some clutch parts if the price is right
Maybe a D crank with a D jug