1999 225 carb backfiring thru bleed system

[dwjr567]

I have a 1999 225 carb that is backfiring out the bleed system on the #2 cylinder off idle it seems to start around 1200 rpms. It doesn't start right away it takes a few minuets when running it on the hose I have not tried it in the lake. I have replaced the reed valves. rebuilt the carbs twice when rebuilding the carbs I have not replaced the jets needle and seats or the floats all seem to be ok. Ran it on a separate gas tank with no change. Went thru the entire bleed system and found a check valve sticking replaced the valve no change. The last thing I just noticed was there is gas around the air fuel idle screws. could they be worn out. It doing bad enough to burn the bleed hose. I have completed a compression check all the cylinders were at 95psi. I also put in a new water pump

Thanks in advance for you help