Jaffa, i was going to suggest the bottom oring but Bruce beat me to it.
As to why coils crap themselves that's a good question, i've never stopped to think about the why. On the bright side of that though is a regular TVS series tecumseh coil is reverse compatible with with the type that's fitted on the VLV/Ultima motor.
Now to deal with your revving issue. I will assume that the butterfy in the carb operates freely and is not binding. You will find the crankcase ventilation breather hose coming "through" the path of the governor linkage and plumbing into the top of the carby. The hose has to be re-routed (i can't remember if it's over or under, but what looks like the logical path at first glance isn't) to the carby so it doesn't interfere with the governor linkage and hold the throttle open.
