I got a bayou recently and well i tried to start it and got a loud bang. The previous owner used the pull start because the battery did not work but i will give you a step by step walk through on what i did to try and start it.
First put the key in and turned it
then made sure the fuel vale was in the ON position
then slid the kill switch to the left
put the choke all the way to the right
pushed the throttle in and out trying to get some fuel going
then tried a couple of times neutral light coming on for split seconds
i am only thirteen and do not have a lot of man power
and after a long time i took all the energy i had left grabbed the pull start with both hands and pulled it and BANG! I got so scared i took the key out and ran inside. Please tell me good news thanks

 

Please help

 

You have probably "flooded" the cylinder with fuel, this collects in the exhaust and when it finally does fire the fuel in the exhaust catches fire with a bang. "Pumping" the throttle lever doesn't give excess fuel on a quad, putting the choke to the "on" position does. You won't have done much harm. I would get a battery, it will make life easier.