flooding on no 2 cylinder, black smoke

[hardrock]

Hi all
yesterday morning I started my 99 B12 with 30000 miles to go to work, set off and got half way down the road and it lost a cylinder.
Limped it back home and checked it later and no 2 plug was wet,fitted a new set of plugs and started it up and it went back on 3 cylinders.

Took tank off and checked for a spark, all ok took plug on no 2 out and it was wet.
Dried it put it back in and drained no 2 carb and started it up again, it ran on 4 but was black smoking like hell.
Took bottom off the carb but couldn't see anything obvious.
So my question is "Is there a common problem that causes the carbs to flood?" the float needle looks perfect as does the seat and the floats couldn't see any big lumps of crud so im stuck (and annoyed)
Cheers
Jonathan

[99er]

If there is no obstruction of the float and the float is gas-tight (floats), you have to pull the carbs and check the float pin and seat. Draining the carb 'usually' gets rid of obstructions here. Also note that the seat fits into a simple hole with only an o-ring. My '99 at 22K started leaking around the seat on #4 enough to shoot raw fuel out the exhaust. Check the "fit" of the seat brass. If really loose, an o-ring is needed.
While they're out, you can give them a real good cleaning and inspection.
Marc/Atlanta

[hardrock]

Thanks for that Marc, I'll have a go at o rings as I can't see anything else wrong a full set makes sense as the others will be waiting to fail.
Off to the dealers