Motorcycle Repair: honda carbs, valve stem seals, gil gil

Question
i have a 1981 cb900f the no. 4 carb is flooding  when the motorcycle idles fouling out the no. 4 sparkplug so i put a good plug in. it fouls out also so i pull the plug to check if there is spark it sparks just fine so i pull the carbs and change the float and cut off needle if thats what you call it and i changed the slide it still floods and i adjusted the idle jets just like my clymer said to so now i'm going to try cleaning all things that have to do with the timing then see what happens. when i ride the bike it seems ok most of the time then you hear good ole no. 4 spit back then it run just alittle off. there is one thing i have not done to it yet but i don't think its the problem that synchronization. I hope you can help me out when i started this i had a full head of hair i've pulled about half of it out so far. ha ha ha
Thank you for your help.
Gil  

Answer
Gil, a lot of things can cause fouled plugs, including the carbs.
Low compression..
Oil getting past worn valve stem seals/rings.
Bad spark plug cap (5k ohm is about normal).
High float level 15.5mm is standard.
Leaking O-rings in the fuel metering system.
Sinking float... yes, even the solid plastic ones.
Bowl vent passage in the roof of the float chamber plugged up.
Worn slide needle.
Carbs out of synch.
Mixture screws out of range or idle circuit metering holes plugged.
Main jet holder emulsion tube holes plugged up.
Air bleed passages in the carb throat plugged up.
Corroded wire connections for the coils

Hope this gives you some new clues...

Bill Silver