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Sparkplug colours

Posted: Mon Apr 06, 2009 7:58 am
by RogerRust
I'm a great believer in making a close study of spark plugs to gain an indication of the engines state of tune and condition.

The plugs from the MG have a nice pale brown centre insulator and are not at all oily. However the end of the threads are a bit black.

Do you think it's running a bit rich or does it just need a good summer run out to blow away the cobwebs?

<br>Image<br>

Posted: Mon Apr 06, 2009 10:44 am
by millerman

Posted: Mon Apr 06, 2009 11:04 am
by d_harris
Really useful link there Millerman. Thanks

Posted: Mon Apr 06, 2009 2:51 pm
by dalebrignall
mine are like that id think they are ok for unleaded fuel.they reconed when you had 4 star petrol the end of the exhaust used to go grey after a blast,but not any more with unleaded fuel

Posted: Mon Apr 06, 2009 10:12 pm
by bmcecosse
I would say it's 'just right'! Now you should do a full throttle run up a long hill, and near the top switch off and drift to a halt. Whip the plugs out - and see what colour they are under these conditions.