What should I Check? Carbon on Plugs.

My question is Why is #1 and #2 plug black? #3 and #4 are buring good slight brownish color close to new looking. I checked float levels after the carbs were taking apart to check for any dirt. The carbs were rebuilt all good there. It shouldn't be the ignition/timing cause 1/4 2/3 are whats right. I know air mixture screws only work at idle. I thought float level, then I thought Carb sync maybe? Somethings causing either #1 and #2 to run rich? or #3 and #4 to run lean? I dont have a clue. Possible valve clearence? Dont think so. I DONT KNOW please help. THANK YOU

Try replacing all four sparkplug caps and the ignition wires/cables from the coils to the sparkplugs.

Do one at a time so parts are not mixed.The NGK sparkplug caps contain a resistor that with time fails creating a weak spark.

Another place to look is the primary(small wires) side of the ignition coils. They should read battery voltage is the battery is fully charged.

If the voltage is down to 7-8 volts, your bike suffers from corrosion in the wiring or in the electrical connectors.

The website www.wgcarbs.com lists parts and how to do this simple ignition bypass using a relay.

More than a few riders here have done this to their bikes witha great improvement in starting and combustion efficiencies.

I thought about that but 1 and 4 are on the same coil so plug # 4 should be black too but its only 1 and 2

I guess it could be the resister caps? What other Ideas does anyone have?

I can't tell you how much you need to do the wired george coil repowering. I tried to avoid doing it for a while, but when I did I immediately witnessed performance gains. If 1 and 2 are fouling, I might look to carb settings. Are you starting it on its side? this will through of the carb float bowls. 1 and 2 would receive more fuel because it is lower than 3 and 4, and 3 and 4 would resultingly run lean.

How are your valves, seals and guides? Could be leaking oil past or it could be running rich on 1 and 2. On my 900 Plug# 1 is black always while the others are good. Looking at doing a top end job this winter to see what the issue is.

No I always mount the bike and level her. Then start. Unless I want to check other things, then its in the stirups(center stand)What ever makes her happy

I haven't had the carbs sync yet. I did go out and fine tuned the carbs 1 and 2 (adjusted the pistons down) and what a BIG difference, Idles better quick throttle response I will check plugs out when It cools down(dont want to mess up the treads) I checked the voltage to the coils and only go 10 1/2 volts, so I will be doing the relay change over soooon. Plus still running points. I will be changing to Electronics soooon. So far running pretty good for an old gal.

Can you turn the 2/3 coil around and put the #2cap on the #3plug and the #3cap on the #2plug? If so, and if plug #2 still soots up, you can eliminate the possibility of the coil/sparkplug wires/plug caps. Ed

I will give it a try. Maybe I need to replace wires and resistor plug ends..They look like original wires.30 plus years on them.

If not already done, would also assure correct valve clearances.

Good Luck!

Patton wrote:

If not already done, would also assure correct valve clearances.

Good Luck!

Amen, I second this suggestion!


I hate to do valve clearances!:blink: