all 4 plugs fouled; ideas please

[trispeed]

Hi, I have a 1981 GS1000G with 48k miles. New to me for a couple weeks now. All stock, I noticed poor running at 6000 feet elevation today, bike wouldn't pull clean past 6ooo RPM, it would hesitate and sputter a bit. Got a little better after returning to sea level. Decided to change the plugs and clean the (K&N) air filter. After doing this, the bike wouldn't pull past 2000 RPM and fouled all 4 new plugs (within a minute of running), black and sooty. I've checked all the electrical connectors, cleaned the carbs (again; all stock jetting and needle position) tried it after cleaning the plugs without the air filter, ran a little better but fouled them again. Is this indicative of some sort of ignition situation? I can't imagine all 4 plugs fouling equally from a fuel system standpoint.
Thanks.

[chef1366]

What's up guy over the hill. Try charging your battery. Your battery might be bad. Move from there to cleaning grounds. Then, your charging system. I'd have to agree about your carbs, unless you've won the CA lottery it's probably electrical.

[trispeed]

battery's good, charging system's fine, etc. etc.
I won't be getting off that easy.

[Road_Clam]

Hi, I have a 1981 GS1000G with 48k miles. New to me for a couple weeks now. All stock, I noticed poor running at 6000 feet elevation today, bike wouldn't pull clean past 6ooo RPM, it would hesitate and sputter a bit. Got a little better after returning to sea level. Decided to change the plugs and clean the (K&N) air filter. After doing this, the bike wouldn't pull past 2000 RPM and fouled all 4 new plugs (within a minute of running), black and sooty. I've checked all the electrical connectors, cleaned the carbs (again; all stock jetting and needle position) tried it after cleaning the plugs without the air filter, ran a little better but fouled them again. Is this indicative of some sort of ignition situation? I can't imagine all 4 plugs fouling equally from a fuel system standpoint.
Thanks.

Do a compression test. I about guarontee you have weak piston rings. 48K is definately near the end of an engine's top end lifespan.

[rustybronco]

Hi, I have a 1981 GS1000G with 48k miles. New to me for a couple weeks now.

All stock

I can't imagine all 4 plugs fouling equally from a fuel system standpoint.
Thanks.

New to me? black and sooty=fuel black and oily=oil burning
double check jet sizes and settings did he change needles? drill out the jets?, p.o. did what to it? who knows...

[trispeed]

New to me, I have owned it for 2 weeks. Ran great, though the fuel economy has fallen off in the last 3 tanks worth from 150 mile to reserve to 140 and the last, 125. Sorry, I thought I stated in my post; all stock, the jets are stock, 115 main and 40 pilot, the needles are in the stock position, the air filter is clean, as are the carbs. New plugs gapped properly.
We are looking for something that would affect all 4 cylinders identically. Compression, carb problems would not likely affect all 4 at the same time. Coils wouldn't usually fail at the same time. What affects all 4 equally? Must be ignition before the coils?

[nabrams]

Have you measured voltage at the coils?
If both coils are getting below-par voltage (less than 11 volts) that would results in very weak spark across the board. This in turn, would lead to poor combustion and make the plugs black.

[chef1366]

CDI unit(Igniter).

[trispeed]

Thanks guys, I'm going back and forth to the garage as we speak!
Compression test reveals 139, 132, 125, 135
not great but servicable according to the manual.
checking voltage to coils now........

[trispeed]

voltage at the connectors going into each coil is 10.8 volts

[flyingace]

If everything else fails, see if you can find a stock airbox and filter. Usually, aftermarket intake components will create a lean condition, but it might possibly work the other way, especially since you've left the exhaust stock.

This is something that would effect all cylinders.

[trispeed]

the K&N filter is in the stock airbox. I would have mentioned it if it were the pod type that does indeed muck- up the intake workings.
Thanks. I have a super rich condition with all 4 plugs fouling instantly.
I am going to try to find an ignitor box. If that proves to be the culprit, I will change out to a Dynas S system with coils. Any feedback in that regard? I understand that my '81 has a mechanical advance unit, so the Dyna S would bolt up.

[chef1366]

Check the strength of the spark at the plug itself.

[trispeed]

yes, though this is very subjective. There's what I would consider a hairline sliver of a spark.

[flyingace]

Is 10.8V enough to the coil? Sounds low, but I don't really know. What is your battery voltage reading?

Maybe Earlfor will bless you with his electrical knowledge.