Motorcycle Repair: Honda Shadow running to rich, air fuel ratio, air leaks

Question
I have an '84 Honda Shadow 700 and it back fires every time I throttle off.  It also smells of gas when I start it up.  How can I adjust this problem?

Answer
The backfiring is actually a lean condition.  It can be caused mis-adjusted idle air mixture, dirty carbs, air leaks in the intake manifolds or a reduction in exhaust back pressure. When a exhaust pipe rusts out or someone changes them for a less restrictive system, it changes the air fuel ratio and can lead to the backfiring you hear. Not sure where the smell of gas is coming from but there could be a leak in a fuel line somewhere, or excessive cranking time loading up the exhaust with fuel.    

Regards,
Rich