Theres not a lot to the HCS engines, i think they have an air temperature sender in the underside of the airbox (its been a few years so sorry if im wrong). Other than that theres the ignition module, and thats about it i think. I personally would say its more likely going to be something to do with the carbeuretor, having been sat unused. They have lots of diaphrams etc, and perish over time, and these things also tend to seize/stick over time when not used.

Sorry i cant be of anymore help?