Anders Elsberg of Denmark has a long history of tuning and racing small displacement engines and the Honda 50 is one of his favorites. Though many tuners and racers of the little Honda will simply increase displacement and compression and add performance cams, Anders didn't want the tradeoffs required, a higher and narrower useful RPM range being the primary problem. High winding screamers go fast but don't last. What to do? Add a supercharger, of course!
The number of blowers suitable for the little 50cc engines is pretty limited and Anders has experimented with them all. Everything from automotive smog pumps adapted for blower use, the supercharger from a Subaru 660cc Kei-car and blowers designed for racing karts. Gearing the blower drive down and controlling pressure is a must but with 1/2 bar to 1 bar of boost the 50cc Honda is putting out between 8 hp and 10 hp, a very nice increase over the roughly 1.5 hp from the stock engine.
Elsberg doesn't just modify the engines, though, he rebuilds the entire bike and when he found his last exhaust was too loud to meet specs he made his own, but instead of welding up various cones he made one using hydroforming, very cool!
Plans for the near future include a 50cc twin. There is quite a bit on his site worth looking through, there's even a photo of a 3 liter 4 valve Lancia/Ferrari V8 destined for a future motorcycle. Hey, you don't always have to stay on the small side of the displacement range.
Anders said he likes to help out the young kids, getting them interested in classic racing as a way to keep them off the streets and out of trouble. What better way than this? Nice work Anders, ... very nice.