#1 cylinder dead (fresh start)

[b717doc]

O.K. Fresh start.....
1982 GS1100GL (z) has new cylinder base gasket, new rings, valves adjusted, has good compression, healthy spark, but wet plug. Can't tell if it's oil or fuel...Removed header, #2, 3, and 4 appear normal inside, but #1 is dark and damp....#1 will get warm on initial start, but never gets too hot to touch, wheras #2, 3, and 4 are piping hot. after engine warms, white smoke develops. All carbs clean, float level checks out (using tube from bowl), bottoming out mixture screws on #2, #3, and #4 carbs will kill engine, whereas doing this to #1 has no effect on idle. Swapped out ignition coils, no help, Spark is not problem....I'm thinking either carb is fouling plug, or oil is fouling plug, hopefully it's not the latter.....

[DimitriT]

Are these rebuilt carbs? Try swapping mixture screws with one of the working cylinders. While you are doing this count the # turns down to stop and compare to the other. Only other thing I can think of is a leaky choke: try swapping that with a good cylinder. These are easy to do things (without removing carbs). Does your bike have Mikuni BS carbs? Check that the rubber pilot jet plug is not leaky.

[b717doc]

I have been through the carbs, everything is crystal clear, and in good working order,,,,,will take apart again tomorrow and see what (if anything) I can find,,,,meanwhile, anyone got any mikuni's they want to get rid of???

[LW_Icarus]

sounds like fuel fouling to me, look for clogged jets or passages in that carb specifically, and also verify no vacuum leaks.

[flyingace]

Something doesn't add up here. You say you have wet plugs and a good spark? If #4 is firing at the right time, then so is #1. Therefore if there's gas and compression - it almost has to fire. Just to make sure it isn't a weak spark to #1, swap leads between #1 and #4.

Is it possible the plug is carbon fouled and not wet? It would look black and sooty, but not wet. There have been a lot of instances where one carb (1 or 4) has been worked on a lot because of corrosion and the needle/seat bind and get stuck open. It can be intermittant.

[steve4mc]

Fouling number one.

Where does the vacuum line to the petcock get its vacuum on your bike? Is it number one? IF so, you could be leaking extra gas back into the carb through the vacuum line. You say it's wet and black. Oil fouling looks oily. Gas fouling smells like gas but it's still black. If it's getting that much extra gas, it has to be coming from somewhere and usually if the carbs have a problem with crud plugging them up, you would think they would put out less gas instead of more. To check and see if the vacuum line is leaking gas back to the carb, take the vacuum line off of the petcock. Usually I take off the other gas flow line two. Put a length of hose on the vacuum line at the petcock. Suck or pull a vacuum on the hose. You will start to hear a gurgle before gas actually flows if there is a hole in the diaphragm. Point the hose down and see if you get gas flowing in the vacuum line. If you do, I bet that is your problem. Hope this helps. (I know it stumped me for more than a year, but mine was cylinder number two.)

[b717doc]

No, the vacuum connection is off the #2 carb, according to bikebandit....will take the darn things apart yet again.....