That's completely normal for any older 2-stroke engine. I have a '00 yamaha 90tlr and twin 120hp mercury force outboards that do the same thing. I just always make sure the ball is firm, the fast idle lever is up, and I'm using the choke. And if that doesn't work I'll take a bottle of ether (engine starting fluid) and spray it into the air filter.
Rubs
January 2009