#4 Plug Fouling

Ok I have had tons of trouble with this bike but I have sorted out a lot of them. I am getting close and I think this may be my last problem.

Carbs are all cleaned out. (i completely disassembled them several times and dipped them in carb dip, boiled them in lemon juice and sprayed them out with carb cleaner as well as running a guitar string into small openings)

Fuel levels are spot on.

Wired george coil mod is done.
New spark plug wires.

I put a new spark plug in and within a mile of driving it starts missfiring. I pull the plug and it is dark brown/black and wet.
Put a new plug in and the same thing happens again.

Any ideas? Is it definitely carbs or could it be spark?

Did you replace the sparkplug caps too? They will fail with time and heat. Most screw onto the sparkplug wires.

Checked valve clearances? Compression check hot and cold?
Air filter cleaned lately? Oil levels correct(not too high)?
Running a good grade of fuel?

Spark plug wires are new dyna wires with no resistor caps.
Valve clearances are good.
Compression is within spec.
Air filter is nearly new.
Oil level is correct
87 octane from BP or Shell only.
Brand new float needles and seats.

I have swapped #4 and #1 wires and no change

Questions ---

What is battery voltage actually reaching coils?

What is visibly observed spark quality with plug removed from cylinder? Fat blue spark?

Are battery terminals clean and cables snugly attached?

Has integrity of ground connection been assured where negative battery cable attaches to engine?

Whay is condition of battery? Fully charged? Holding charge? Specific gravity tested? Load tested? Fluid levels to specs?

Has charging system been tested by measuring voltage across battery terminals at idle (12+ volts) and at 3000-4000 rpm (14+ volts)?

Has test run been done without headlight being on?

Correct spark plugs NGKB8ES?

Answers may help with diagnosis.

Good Luck!

What coils are fitted (green 3 ohm Dyna) ?

What ignition (Dyna-S) ?

Battery voltage reaching coils. like 12.76 with bike turned off. i dont remember what the numbers where with it running.

spark is fat and blue. looks great outside of cylinder

terminals are clean and snug.

ground is good.

battery has been fully charged on a charger. i have tried running it off a car battery as you had previously suggested.

i will test the voltage across the terminals while running again because i have forgotten the numbers

i dont think i can turn off the headlight. (i could unplug it i guess)

multiple sets of new ngkb8es plugs have been used

stock ignition, stock coils(they ohm out to spec)
dyna wires(7mm solid core i believe)

Thanks for the report.

The ignition aspects all seem okay.

Has compression been tested and correct valve clearances assured?

Presupposing acceptable compression figures and valve clearances to specs, and with ignition okay, suspicion points elsewhere.

If #4 carb vacuum nipple supplies vacuum to petcock, a damaged petcock diaphram may allow fuel to be sucked into the carb through the vacuum nipple, causing flooding of #4 cylinder.

If running pod air filters, assure good flow thru #4, not dirty or over-oiled. Some pod designs obstruct entrance to the pilot air passage (usually not an issue with K&N).

If running airbox filter, assure good flow, not dirty or over-oiled or obstructed by anything stored underneath the seat.

If none of the above, suspicion turns to #4:

Pilot screw adjuster;
Fuel level;
Float valves (needle and seat);
Float integrity (bouyancy);
Float assembly (not upside down);
Float operation (not binding or sticking);
Carb pilot circuit.

Good Luck!

On carb with choke plunger (enrichener circuit), sometimes the soft material at bottom of plunger (that helps seal off fuel entry into the choke circuit) erodes, whereby unwanted additional fuel is continuously added as if the choke always remains slightly on.

But that's the last thing I would check in the present situation. And the carbs at hand may not even have this type choke, as some carbs still use the old fashioned butterfly style choke (a real choke).

Good Luck!

ok. compression is good as well as valve clearances.
vacuum petcock is currently connected to #2 carb.
running stock airbox with clean paper filter.
fuel levels are correct
float valves are brand new.
visualy inspected floats they seem ok. no liquid inside them.(i swapped a float from another carb into #4 and no change)
they are not upside down
i cant detect any binding or sticking(i suspected this so i pulled the carbs off just to check it.
I have the air screws out 1.25 or 2.25 i dont remember. whatever the FSM says. but they are all the same and the screws appear to be in good shape.