Honda HMB215 GXV140, doesn't start

My father asked me to help him getting his mower fixed he said it was working fine 2 weeks ago then suddenly stoped working, is a Honda HMB215 that doesn't start. I checked for spark, there is spark, I cleaned the carburetor, the jet all the small holes with carb cleaner and compressed air, add a little gas to the spark plug hole. but still doesn't start. some times it just throw some white smoke trough the exhaust but doesn't start.
any other ideas on what else should I do ??
thanks in advance.