This is not a carb-on-the-tank engine - there is no diaphragm. The symptoms are of a lean mixture - older Quantums DO have a mixture adjstment screw, but most don't. Drain the float bowl (a blob of water in the bottom can patially block the jet and give these symptoms. If not, you will have to strip and clean the carb, running a piece of copper wire through all the jets.
phil_saunders(a)bigfoot.com
Phil Saunders
July 2009