Hitachi 450LC revs high upon starting and dies

My Hitachi 450LC was running fine but now when I start the machine it revs high for a second or two then shuts off. If you turn the key to accaccessories before it dies it will remain running.I had just replaced the ac belt that was broken and tightened alternator belt, and everything was great ac fixed and alternator belt squealing gone. Shut off machine turned key to accaccessories to check out exterior lights. Had switch in accaccessories money for approximately 10 min and then my problem accured. Any suggestions would be greatly apreciated.