GL1500 Stumble and rough idle

imported post

I just joined a day or two ago and have been looking for threads that deal with my problem and wow their are a lot of them, but I can't find just the right one. I have a 1991 Aspencade, 85,000 miles. I have owned it 53,000 of those miles with no real problems. Now it is beginning to idle rough, like it is not hitting on all 6. It has even died a few times at idle. It smooths out around 1500-2000 rpm and runs perfectly.

I changed the plugs tonight. The old ones (I never changed them before) looked great. No excessive wear and a nice tan color. All were about the same. After the change, no difference. But I did notice than the spark looked very weak-- a lot of yellow and not much deep blue. I randomly checked different wires and got the same result with the weak spark. I pulled the wires from various plugs on idle and every one impacted the idle.

I understand that my problem could be caused by anything from dirty filter, dirty carb to bad coils (how do I test those). But I don't think that it is bad wires (I have ridden in some horrific rains recently with no negative impact on performance). I have run some chevron techron in the fuel. But the weak looking spark is making me think electrical.

How about the battery? It starts just fine, (except it won't start until I unpress the starter button) but if the battery is not 100% could that be my problem. Any diffinative voltage tests that would get me anywhere? If I hooked a charged battery up to it with jumper cables while it was running, would that tell me anything?

One other thing, I noticed that I had quite a bit of oil around my alternator. Is that normal on these bikes? I have never seen it drip, but there is oily dirt all the way to the bottom of the motor below the alternator.