What Does This Plug Tell Us?

My 97 Thunderbird 900 has been running g rough for a while now. Compression test was good. Carbs have been out and cleaned. New filter. New plugs. One of the coil packs has been replaced.

The right plug keeps oiling up. After only 3 or 4 runs of about a half hour each it looks like this.



Does this suggest anything to you?

I'm going to switch the coil packs around to see if a different plug is affected.
I wonder if it's a valve issue?
Maybe the carbs need balancing?

Thanks.

 

Spark plug test.
Does the spark look right?
https://youtube.com/shorts/-B-4U5ptj1A?si=T79OsFhD7baMN1-q

 

I have not.compared.it with the other. A good suggestion. I have Swapped the coil packs round though. If a different plug fouls we know its electrical. I've been in touch with Paul Messenger and may well get the stick coils if I can pin down this issue.

 

Bike starts well with a clean plug but gets progressively grumpier over a few days. Fouled plug. Riding to work and back today she pulls well but is a bit iffy idling and occasionally stalls. I wonder if she is running rich, particularly on that right cylinder. When I cleaned the carbs i didn't touch the fuel mixture or balancing. Something new to learn. I'll pull that plug when I get a moment to see if it the same one fouling even though I've switched the coil packs. My (latest) guess is it is not electrical.

 

Yep. To me too. Not wet. Google seems to think that is a symptom of it running rich.