[ophic]

My mrs' Honda Shadow was running terribly after not being used for a while. This turned out to be gunked up carbs and the local bike shop ran them through an ultrasonic cleaner. After this it's been fine.

The main cost was their time for removing the carbs. If you could get the carbs out yourself, I'd imagine it'd be quite cheap. In fact, you can buy the ultrasonic cleaners for not all that much.