It should run without the power valve connected, some people block them off entirely.  I doubt it will run as well, though.  Without the spring it doesn't sound like the valve is locked in position, which means it may randomly open and close, which would affect its power delivery.  I would just be sure you didn't drop any parts in the engine, because that could be catastrophic.

I recommend you try fixing it yourself.  The parts are probably not that expensive new (if still available) or you might find them used on ebay.  You can also access the power valve mechanism from the rectangular site glass, so you shouldn't have to remove the entire cylinder.  Good luck.