If you own a 4-wheeler you should know that they can sometimes just not start here is a article that might help you some its about the easiest way I know how to explain.

[edit] Steps

First you will need to get it out you can use a ratchet or another tool to unscrew the nuts and bolts that hold it in your 4-wheeler.
Take the bottom part of it off with a wrench or ratchet.
Find some WD-40 and starter fluid.
Get the bottom off with a wrench or ratchet get a compressed air hose also.
Spray WD-40 in all of the holes and then blow it with a air hose.
Know that once you have done this it should crank if not try to choke your 4-wheeler.

[edit] Tips

Starter fluid works well on just about ANYTHING on your 4-wheeler!
there may be some extra screws like really little ones that you would have to use a Phillips head or Flathead screwdriver on.