If it has an air filter housing like this one it's probably not priming. Remove the filter and press the primer bulb, you should see gas squirt into the carb. Several times when I have removed the air filter housing to clean carbs and have not used a new carb/housing gasket it has not sealed well enough to allow the primer to work. See this video
https://www.youtube.com/watch?v=NFMGKUT7BnA
Cannon