Cylinder #1 spark plugs Rotax 912ULS

Since my first engine start I've noticed the plugs in Cylinder #1 are black (sooty) compared to the other 3. I was hoping it was just something that was happening because the first hour or so was mostly idle to 2500RPM. I had the 25 hour inspection done by a Rotax certified mechanic. He said he's never seen it before on only one cylinder. The Rotax response has been not to worry about it as all engine parameters are good and it runs fine.
It may not be connected but I also noticed the exhaust is very sooty. I had a 912 in my Pulsar and never had the issue.

Carbs are balanced
Only run 93 auto fuel (normally 5% ethanol)
Cleaned and re-gapped the plugs
Compression was perfect (25 hour check)
The other plugs are a nice light brown

The plugs are not oily at all, the soot (maybe carbon) wipes off.

Has anyone else seen this issue, if so any suggestions on what else to check.

Thanks
Gary

Fronnt two on mine.

Lockwood says not to worry about it, that it's pretty common, and due to front cylinders running cooler when not producing cruise or max power.

Wayne 120241/ 143 WM

Have noticed the same on the #1 cylinder. No worry.

It is normal and happens at idle settings and it can move from one plug to another. You can run the engine up around 4000 rpm for 2-3 minutes then immediately bring it back to idle and turn the engine off. no idling. The black will be all gone. you should never judge how the engine is running after an idle.

912ULS spark plug color

Thanks to all for the replies. Seems like it's not an issue, I will try what Roger suggested just to make me feel better.

Thanks again
Gary

Soot on Rotax 912 plugs

I have over 800hrs on Rotax 912s. This normally happens when you run at idle too long or below 5000rpm too long. These engines love to be run and will be at their smoothest and best at about 5200rpm or maybe a little higher. They will do some weird things sometimes if not run hard. Not to worry at this point, just run the **** out of it.