What pipe do you have. Since you changed the jet it quit running off didnt it. I fought this same problem with mine for awhile. The biggest thing help mine was I took the ex flange off and put the new gasket on Behind the flange .Then I clean ex flange really good cleaned the pipe out really good. Then I used  honda bond on my flange and inside of the pipe. Then I let it sit till it completely dried.  Which stop all the leaking the motor then I figured out my jetting.   Which took awhile . Do you have fmf pipe and silencer.