Is it normal that on my 1999 Flstc EVO, I can hear sometime expecially when the engine is cold, some bangs coming from the umbrella valves, and I feel a lot of air coming out from the air filter
This can also be caused by a leak in the intake manifold. Or a leaking vacuum line from the carb to the petcock (if your using the stock vacuum petcock) Look for this type of problem before changing jets, as uping the jet could just mask the problem and not really fix it.
Good Luck!
Dave