Black sooty dry sparkplug

Hi all. I have a 1983 xj750 Seca.
I recently had the bike in the shop and had a service and synchronization of the carbs. Bike runs OK but is hard to start cold. I replaced sparkplugs today and noticed that the outer sylinder plug on the throttle side is sooty,dry black. The rest of the plugs are fine. I don't want to start adjusting on the carburetor but are wandering if one sparkplug can be bad or if something else is wrong.
I appreciate any advice on the subject

 

You're going to have to. A bad sparkplug would be wet and not at all sooty.
Given that she's hard to start when cold, I'm suspecting that cylinder (at least) is a tad rich.

 

Thanks k-moe . I am a dummy with carburetors . Is there a detailed description /pics of where adjustment screws are and which one to turn in or out?
There must be one for air and one for fuel? If I can get instructions for dummies I will try

 

https://www.xjbikes.com/forums/threads/owww-my-eyes.112790/

Second photo down the page. To the right of the enrichment circuit plunger, right behind the post that holds the enrichment circuit rod, is a small hole with a small screw. That's your idle mixture screw.

 

Thank you so much kosel
I will try to adjust. Is it in or out for a leaner fuelmix.?
I ordered a kit from gunson. It's a sparkplug with a glass plate which allows you to check the combustion color and adjust the fuel/air . I'm exited to try. Will come back with a happy end I hope.

 

In=leaner, out=richer

 

Thanks Chitwood.