Our club president just went through a bent needle valve on an O.S four stroke. It wsn't badly bent, but you could feel it drag as it got near the sweet point. In theory this shouldn't be a problem but I was, What I think was happening was that as the interferrence maximized, it pushed sideways and the O ring lost some of it seal, if not all.

I've got a few different O.S engines both four stroke and two stroke. Most of them would work in a pinch as the tread size and needle length were the same. What was different was the taper on fineness of the point. That would change the sensitivity of the adjustment. THe other difference was the extention on the outer end that let you attach a long extention to the needle valve, IE a hole for a wire and a set screw to hold it.

Compaire a couple needles from other engines to see if they might not work. The Magnum engines use just one part number for almos their hole line of engines, even though the ones orginally in the engnie may be different from the Replacement part. IE the Mag 52 has a stubbyer taper compaired to the replacemnt needle, or one from a Mag 61 two stroke. The replacement works better for fine tuning the engine.

Don