Sooty plugs

[Stanmo]

I checked my spark plugs today and they are all quite black with soot deposits. I have a 1098 Morris which I add a supplement to the fuel when filling. I’ve checked the air filter and all is well. The car runs ok although in my limited knowledge I think it sounds a little slow when idling. I understand that this could mean it’s running rich? Choke is completely off. I have no colour tune just determination to learn. Could anyone advise on steps to remedy the plugs ?

[paul 300358]

How far had you driven before looking at the plugs? Just starting the engine and backing out of the garage will leave them black. You need to get the engine hot, turn it off and allow to cool before removing them.

[Stanmo]

Hi Paul. I’d been for a good 20mile run and had just got back to do a few checks, so she had cooled down. It’s the first time I’d checked plugs since buying and over the past week have been enjoying the weather using her daily.

[Stanmo]

One other thing? Could a blowing exhaust have any relevance?

[myoldjalopy]

I can't see how - but fix the blow and you'll find out! Sooty plugs are normally a sign of a too rich mixture. There may be sooty exhaust smoke as well. Less likely is that the ignition is a bit retarded. Less likely again is the wrong plugs.
You could try adjusting the jet mixture nut when the engine is hot - screwing it down will make it even more rich and the exhaust note will become rhythmic, known as 'hunting'. Then screw it up (weaken the mixture) until you get a smooth idle. If you weaken it too much, it will start sounding 'splashy' and irregular.
If you haven't had the car very long it would be worth checking over the points, the plug gaps, valve adjustments and timing - who knows what a previous owner did - or didn't do! Only if all these things are correct will you be able to make optimum adjustments to the mixture strength.

[Stanmo]

Thanks Myoldjalopy, I cleaned the plugs and checked the gaps etc, noticed that the choke cable although off wasn’t actually returning back . I mean the mechanism on the carb. I had to shut it off by pressing it. Took it for a good run and plugs were biscuit brown on checking. So I’m thinking this issue could be the choke was slightly on all the time. Anyway I have no idea how this should work as I can’t find a diagram of the set up to adjust or see if any thing is missing. I’ve attached some images to show.

[myoldjalopy]

Looks OK to me - unless there could be a bit more slack in the cable where it attaches. From what you say it would appear the choke cable or mechanism is sticking a bit, rather than it being a mixture adjustment issue. I would clean and lightly lube the mechanism where the choke cable attaches. That may be enough. And/or the cable itself may be sticking. I had a similar problem - see here: viewtopic.php?f=4&t=73060
It was a faff to get the cable out from behind the dash so you may get away with dribbling a little oil (don't overdo it) down the cable held high when disconnected. As mentioned above, there should also be a little slack in the choke cable when attached to allow the mechanism to shut off fully.

[Stanmo]

Thanks Myoldjalopy, i will have a look at the weekend and hopefully remedy the issue. I’ll let you know how it goes.