More Towny info:
Fowler got an mlm people's pipe on the towny. I'm not sure how he modified it.
The A35 Tomos Biturbo will mount up pretty easily. Just a little Dremel work on the flange bolt holes. I got it to hit with stock cylinder and do low 40s.
When I sent the Malossi Towny engine back to its owner, I told him to try a biturbo. He did and couldn't get it to hit and noticed no difference in top speed over the stock exhaust. He must have had it over-jetted. Hack n welding is a problem with stock header as Yamaha made them so damn long unless you want great low end.
Orange qt50 clutch springs will make it shift at 23-24 mph instead of 18 or so. I used these with the 60cc kit. Don't know if stock engine could get them to shift or you might be able to throttle shift it. You would probably need the Malossi kit to get the black clutch springs to engage. It would be interesting to see where shift point would be with them. Maybe 30mph? (edited)