Just picked up an '05 Met for next to nothing as a flipper bike (I've always thought they were cool) and cleaned the carb, put a new battery and fresh gas in it and got it running. The bike is not making any power - won't go over about 15 mph and I have discovered that the CV diaphragm is not rising as it should. I have taken the top cap off the carb with the engine running and for some reason the diaphragm is being sucked down instead of up when it is revved. As an experiment, I took the spring out and placed it underneath around the needle to hold the slide in the up position, re-installed the cap and the scooter was much more powerful and could almost reach top speed. Just can't figure out why there is vaccum under the diaphragm. Any clues as to the causation of this carburettor canundrum? What am I missing here?