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 Post subject: Spark plugs
PostPosted: Sun Apr 17, 2016 8:31 am 

Joined: Sun Jan 06, 2013 7:40 am
Posts: 245
Location: Cairns , Australia
I reset the spark plug gaps today , when I checked the spark it was a dull white not blue as I expected . could this be a sign that the coil is on its way out or some thing else, one of the plugs is a new one, in the past I have noticed that the plugs are a bit oily. I have a military style ignition system , I got the plugs form Dale at Haflinger Technik they are made by Champion XML -12 any one know how they compare to the original Bosch WC5A/WC225ERT which are no longer available . Is there any way to check the coil as to, if it is working correctly.


 Post subject: Re: Spark plugs
PostPosted: Sun Apr 17, 2016 4:38 pm 
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Joined: Sun Dec 30, 2012 12:49 pm
Posts: 1831
Location: Lewes, East Sussex - UK
Hi Dave,

Quick bit of Internet searching produced this page: ... _PN/XML15Y

From it I found:

Then on to this -

Last one gives a heat range of 112, but the Bosch WC5A has a heat range of 225 - One has to wonder if they use the same heat range standard numbering system?

As far as your coil goes, you need to check the voltage you are actually getting at the low tension coil terminals, then unless you have suitable equipment to check voltages in the region of 20,000 / 25,000 volts you are only going to be able to say, Yes, I get a spark! The colour will vary according to the atmosphere. i.e. air pressure, humidity etc.

If you are consistently getting dark oily plugs then first off, make sure your Carb has the correct size jets, then do a compression test to see if your rings / valves are sealing OK. If those check out OK, then you could try a "hotter" plug, but on the military / shielded plugs, that is going to be difficult. I saw some prices for the original shielded Bosch WC5A plugs on European Ebay and nearly fell off my chair!

Good luck!


Haflinger 703AP LWB 1973 - (Once owned by Lady Sutherland & Sons.) Now called "Lurch" !

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