G'day Bearster. Just wondering if when you use the pull start if it fells like it's trying to turn the engine over, but slipping, or does it feel like there is no resistance to the pull starter (other than the recoil spring). If you have the latter problem it might be the pin in the back of the crankshaft in the engine (I had this problem a while ago with a fairly new GST 7.7)
Check out this link [link=http://www.rcuniverse.com/forum/m_6962143/tm.htm]Pull Start Dramas[/link]
Hope it helps.
Cheers.