Small Engines (Lawn Mowers, etc.): B&S Vanguard

Question
I have a 16hp vanguard V-twin on a cub cadet rider. I just rebuilt the motor (rings/pistons, valve job and all gaskets) along with cleaning the carb. The motor wont start and is back-firing thru the carb. The valves are adjusted to spec and I can't find any intake leaks. Any suggestions??

Answer
Backfiring is very common with incorrect timing.

Were there marks on the crankshaft and camshaft for setting the timing?  Did you re-check the flywheel key?  I have had them shear when trying to start rebuilt engines.

Let me know about the marks on the crankshaft and camshaft.
Eric