Morris Minor Owners Club

Hi everyone, I've taken out one of my plugs to try to check the mixture.
the electrodes are light brown but the ring around the bottom of the thread is black and sooty. It can't be both too rich and to lean, so what is your best guess?
I have attempted to provide a link to a, blurry, picture.
Thanks.
Steve.

http://links.pictures.aol.com/pic/cf10w ... WLTW_l.jpg

I hope that works.

Looks lean to me or perhaps too hot a plug.

I'd generally ignore the base and just look at the element colour.

Under the carb should be a little plunger. This raises the throttle slide, basically making the inlet air more lean.
When the engine is warm and ticking over ok, lift the plunger to see what happens.
When you lift the plunger enough the mixture goes too lean and the engine will go to stall. However in between no lifting and rthe revs evs falling, you should get a very small rise in revs.
If you get a big rise in revs, then it's too rich. If you get no rise in revs, only a fall then it's too lean.

This method is good for standard engines - as it assumes that the idle mixture setting gives correct setting altogether (i.e. engine is standard, everything is working right, and the carb has the right needle)
For a modified engine, it's not always quite so simple to set up.

Always go by the colour of the plug electrodes, the base threads will always be a bit sooty. From the look of your picture, it looks a little lean to me, or a very new plug.

Use the carb piston lifitng pin, to raise the carb piston 0.8mm, if revs drop mixture is lean, if revs rise mixture is too rich. You want to aim for no change in revs or a very slight increase. Be sure not to lift the piston by more than 1mm or the engine will cut out. Running a little rich is better than too lean, which can damage the engine.

Electrode looks white on my screen - but you say light brown - so provided it's not white - your mix will be dead right. If it's running well and idling ok - leave it alone!

Thanks Guys,
Yes, you are right it is a very new plug.
Steve

One last check. If I want to enrich the mixture I turn the nut to the left as I look at it leaning over the nearside wing. Please tell me that's right.I mean correct.
Steve

correct, in other words winding the nut down to richen , but only one flat at a time

But that really only adjusts the idling mixture and has very little effect on the overal running mixture.

yes
but the question was what way to richen

Down - simulating the choke action. But little effect on running mixture unless wound down LOTS!