Get your stuff together, Stoopid.

What could cause a motor to start and rev its tits off to 5k (and up) except a major air leak? I can’t find any

The T250 is quite happy to go and stay in the red zone (8-9k) so 5k is like half-throttle setting?!!??

As far as I know the choke plunger can’t be the culprit as it opens a fuel passage… it does work but at these revs not enough to choke the engine down. The idle (air) screw doesn’t seem to have any effect.. but again at that range…