The BSA A7-A10 Forum

Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: duTch on 01.03. 2014 00:27

Title: Reading Spark Plugs
Post by: duTch on 01.03. 2014 00:27

 Wasn't sure to put this here, or in ' Carbies '....

 Whilst looking for the 'Spring rate calculator' in a different post I came across this.....

   http://www.wallaceracing.com/plug-reading-lm.html (http://www.wallaceracing.com/plug-reading-lm.html)

Title: Re: Reading Spark Plugs
Post by: KeithJ on 07.03. 2014 19:04

From what I understand, modern petrol does not give the same "discolouration" as that used in years past.  Again, I have been told the only way to check the mixture "correctly" is by using a lambda sensor.  One other issue with modern plugs is the ceramic is not glazed.  This can be an issue with carburettor engines as the can flood the plug with fuel and cause it to misfire.  Better with modern plugs to put them into a "warm" engine as this will enable the ceramic to get coated with carbon before being next flood with petrol on a full choke.  Problems I had usually resulted in misfire.

ATB  *dunno2*