If that's the case, I wouldn't even try to fix it myself. I'd load it up & take it to the shop. Unless the gas was drained the carb probably needs replacing(internal & external gaskets probably dried out by now) & any rubber fuel lines are for sure shot, along with the fuel filter.I'm sure it worked fine the last time it was used. I'm also sure that no one has used it in 15 or 20 years. Maybe longer.
I know you don't drive, so getting it to the shop might be a hassle. If you helped tear those Harleys down, maybe you can rebuild the carb. My guess is that it probably has a Vanguard twin cylinder engine, maybe 20 hp......good engine. My chipper's about the same vintage & has been sitting about the same amount of time; it won't start, either.

