Gasoline engines when they are not in use for a long period of time they are very difficult to start.

Today I had this problem

To solve it follow the procedure

1.- fill your tank with gas
2.- Remove spark plug
3.- Choke on & turn engine with starter for 30 seconds
4.- Choke off & same procedure as #3
5.- Install spark plug & cap
6.- Ingnition on Choke off & flip propeller

Mine started at the first flip.

Good Luck