R75/5 jetting for Siebenrock kit

[Duane Ausherman]

Ken, that could be the case, but then just how valuable is riding it into the garage and then looking at the plugs?

[barryh]

Hmmm, didn't I read somewhere, probably here, that plug chops don't tell you much with 'modern' gasoline, i.e. ethanol laced?

Ken

I agree, you don't seem to see subtle changes in the insulator colour as you used to with leaded fuel. Gross mixture changes do show up but it's much easier tell if the mixture is grossly too rich rather than too lean which is perhaps not much help here. One things for sure my plugs don't read like those fancy charts you see on the internet. Where I do see changes is on the flat ring of metal at the end of the plug. I have had a real example recently after fitting new floats. With the old floats and a rich mixture I was seeing significant carbon build up and now with the new floats just a light colouring which I believe indicates the mixture is close to correct. At the same time I saw very little noticeable difference to the insulator colour. I think if this base base ring doesn't show any carbon build up at all then that would indicate a mixture that was too lean. I'm generalising here because I didn't do plug chops which you need to do to be sure the effects are attributable to the desired carb circuit.