[quote=Timmyd] for the muffler scrap it it kills hp to take it of you will have to take off the gas tank and carb first . instead off a muffler use straight pipe it will give you more hp and it sounds awesome
This is up to you but I don't really like running straight pipes. The lack of any back pressure in the exhaust has a tendancy to burn exhaust valves over long periods of time. Also remember that if you want to run straight pipes you are going to have to richen the fuel mixture, because free flowing exhaust also makes the engine run lean. We have always used mufflers on our go-karts and never had problems, even revving 5500+ rpm (with a stock engine minus a governor, this gets a little scary
). However, we run 8hp Briggs and Tecumseh engines on ours. As for extra power, you won't be able to feel much of a difference, unless your muffler is totally plugged up and this rarely happens to 4 cycle engines (2 cycles tend to have a problem with this because you must mix oil with the fuel, too much plugs them up). If you really want more power, you need more motor. It looks like a fun project though, good luck with it.