I had a 84 that did the same thing and found that exhaust was leaking so was starving for air but there could be many problems fuel restriction carbon timing which can cost you a motor if it is wrong. There is no one answer but the way I found my problem was running without cowling on and ran fine. I now have a 120 doing some what the same thing starts and ideals but when I put the throttle to it just bogs down some times come up slow. If find something good let me know it might help me thomas.burns3@us.army.mil
