I've heard of people doing this to a honda carburetor such as the ones on 4-stroke mopeds and dirt-bikes, which are all pretty much the same design. Then some people tell me it's not a good idea, and could wreck it. Since I get everywhere on my junker PC-50, wrecking it would leave me immobile, or paying out the nose to bus it to work every day. The longest trip i've made to date is 150 km's from hamilton, ON to Barrie, ON, 5 and 1/2 hours including getting lost in Toronto, and a couple times i broke down and had to clean the spark plug. Cost for gas? somewhere between $2 and $3 canadian. While there, i scored a used engine and made it home with absolutely no mechanical failure. I do want more speed, to make these long trips a little less long. I talked to a guy who had the same moped going 60 km/h with the carburetor modified in some way. I heard from most people that these mopeds are made with an extremely small carburetor and exhaust, which is true - the hole at the end of the stock exhaust is only a bit bigger than a pencil and the carburetor is something like 7 mm. I put a straight pipe exhaust on and it feels a bit faster than stock, and definitely sounds better.