David, the same thing happened to me, those bolts are made from the finest butter!

However mine came straight out. Just get something sharp in there so it can grip it and you too may be lucky, maybe some sharp pointed tweezers will turn it?

Definitly worth a try before you start swapping bits between engines.

 

Smack of a punch & drill it dead ctr 1/4 cm - then drive in an ever so slightly bigger torx bit nice and gently
until it's in there nice and firm then back her out easy you could even add a drop of epoxy to set the torx bit
first -

there's not that much torque holding it in.

 

I took it to an engineering shop down the road and they only charged R20 (about $2) so I'm a happy camper. Put it all together and fired up nicely. Only odd sound now is the leaky exhaust (at the back where the end cans slide in) I'm not stressing about that though, the engine is sounding great and if it wants to leak on the exhaust so be it. Time to ride this thing instead of working on it all the time. Had a shake down yesterday and she hit 200kph on the highway onramp !!

I suspect its ok now