Motorcycle Repair: 1981 Honda CB750C - Exhaust popping, honda cb750c, lean mixture

Question
I recently bought a 81 Honda CB750C which had sat for about a year. My friends took apart the carbs and cleaned the jets, diaphragms ... etc. The bike runs really well but I do notice some "popping" in the exhaust when I back off the gas or down shift. Should I get the carbs synched? Is the popping a sign of a lean mixture and what can I do to adjust it?

Thanks,
Kenny

Answer
Kenny,
it wouldn't hurt to have the carbs synched,
the cb750 runs a little rough when the carbs
are off tune.
Some popping may be normal, if the exhaust
has been modified that would increase the popping.
Engines need some backpressure to run in a
civilized fashion. Make sure your intake tubes
and exhaust pipes are not leaking.
Maybe it needs some new exhaust gaskets.
A lean mixture can be caused by an intake air leak.
or air getting into the exhaust header
can cause backfiring.
If your spark plugs are a very light color after
a hard run you may need a size larger main jet in the carbs.