20 years??? Yikes! Was the bike inside or outside - in a garage? You are very likely to have significant rust buildup in at least one cylinder due to long term moisture build up through an open exhaust valve - even in a garage, I would expect some condensation. You can check quickly for seziure by just trying to turn the engine over with the kickstarter. If it won't move, you may have a bigger problem. It is also likely that the carbs will need a complete cleaning because unless you completely drained them 20 years ago, the gas would have dried in them and shellacked the float bowls. Just some things to stress out about.

No matter where you go.... There you are. - Buckaroo Banzai, 1984.