1999?...
Well, if it's a 99, it could be the GSX limited with the 951cc. This engine is a carbed engine. If you think you might have the GSX RFI, then you have fuel injection. These two different type systems should be the easiest way to tell what engine you have.
But the very easiest way is, ......what side the engine lies on. If the engine cants to the Port (left side), it's the 951cc. If the engine cants to the Starboard (right), then it's the 787cc.:cheers: