If the freedom of speech is taken away then dumb and silent we may be led, like sheep to the slaughter.

- George Washington

Thursday, 12 August 2010

Plug chop

Well, not so much a chop as a quick whip-out-and-have-a-look.

After a couple of hours of whizzing round town and a leg-stretch on the A40, I got home and pulled the plugs to see how things were cooking in the Bonnie's insides. I was expecting a black, sooty mess. Instead, I got this:

It's a poor photo (iPhone camera), and it doesn't really show the colours properly, but the results were good. Both plugs were an even pale brown, one slightly darker than the other, on the insulators and the tips. No signs of overheating, fouling or over-richness. Pretty much what I would expect from an engine running the correct mixture and in the peak of health.

I am going to be on the road for most of tomorrow, so maybe I will get the chance to do a roadside plug chop to see what it's like at 3/4 and full throttle, but it looks as though those 140 main jets were in the right zone, at least.


  1. I could lend you my Gunsons Colourtune! It was completely useless on my old Yamaha 2 stroke...

  2. Would that be a Colortune? Even British products have to have American spelling these days (and the Colortune isn't a recent thing, I know that). I have one - in fact, I have owned two. The first one, bought when I had a troublesome Triumph Dolomite, did absolutely nothing. I mean, it worked, but tweaking the mixture had no discernible effect on the device and I threw it away. I don't know why I bought the second one. Triumph of hope over experience, I suppose. It is still in my garage, but the constituent pieces are in a variety of locations, so if I wanted to use it I couldn't. And it's the Bonnie's mixture at half to full throttle that I am interested in, and I don't think the Colortune does that.

    Yup, completely useless.


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