i have a 81 suzuki motorbike, i've got it to back fire but i can't get it to start... can someone suggest any

sounds like the timing is off.

l have a 2001 and it does the same thing since l ran it hot..i warped the cylinder head on it..if the head is another color(slightly red) then you would need to take the head to a machine shop and get it milled down in order to start your bike again. whats going on is now you have no compression in the engine to start the bike, so the gasoline is just pouring in the cylinder and the spark plugs are igniting the gas and the engine wont turn over enough to run..