Seems to be lots of bitching going on in this thread, don't really know the history on this, but guys sort it out elsewhere?!
Anyway if its the reason behind sticking 51mm(or any oversize throttle bodies)butterflies is still the topi of discussion then I'll continue. I believe the problem lies in the shut angle on the edge of the butterfly itself, any OEM butterfly will be machined to an elipse, with the oposite sides displaying apposing angles that will seat completely flat on the throttle body inner wall as it closes. This allows a good seal allowing the bypass valve and idle stabalisation valve to do its job properly. Many of the modified THB(mine included) seem to have a square edge to the butterfly meaning the the butterfly valve does not close cleanly on the THB inner wall, and quite often beyond the throttle posistion sensor close position meaning a tricky set-up. So to the reason for the sticking open phenonemon is because the geometory to the closure is not correct, which leads to it sticking from time to time.
To Fix it you can either machine a new butterfly correctly( not easy if you don't know the specifications) or depending on availibilty to doner spares fit a butterfly from another engine which meets your THB size. I'm still looking out for something suitible, but basically anything with 51mm standard THB would or should do the trick. I'm yet to find anything suitible, but tbh I've not looked that hard because Idon't see it as a major issue.
