Sucking air in through exhaust?(not xs)

[Mitchell_p]

I just did a top end rebuild on my daily ride (not xs) It's a single 600 cc and don't know if I've got the cam around the right way. When I try to kick it over it sucks in air through the muffler instead of expelling it. Does this mean I have the cam around the wrong way?

 

[CDNTX650]

sounds backwards...

 

[bloodthirstysystem]

drill a hole in the exhaust pipe and run a fuel line to it. throw on an air filter on the muffler. it will be badass