Acouple of weeks ago I bought this motor and went to the guys house to check it out. It started right up on second pull. A long story short I bought it.When the guy I bought it from was showing me how good it ran the cowling was off.It really sounded good and ran great in the barrel. When I got it out to the lake , it started fine but could not get any power out of it. Just for the heck of it I took off the cowling and it ran great. It was a nice day at the lake so I kept the cowing off untill I went home.Why dose it run good with out the cowling? And run bad with the cowling on. Thanks for any help.
Exhaust leaking into the cowling is common on those buggers. Could be from the exhaust relief hose or from the midsection. Use the search - that condition has been documented a few hundred times around here. A lot of people just run them with the cowling off.
Do a search on the forum, this topic has been discussed many times. To make a long story short the motor is sucking it's own exhaust in through the carb, there is a leak somewhere, several places are suspect.
Signature- If you have fuel and spark- Have you checked compression?