Mixture

[minor65]

I know this has been covered many times, but here goes.

My minor's mixture i thought has always been correct. I removed the new spark plugs which i fitted about 100 miles ago (at headgasket replacement) and they are a lovely biscuit colour. Though in the BL Minor handbook it says that went you lift the piston in the carb with the pin underneath the engine should rev up slightly then the mixture is correct. And if the engine dies then the mixture is to weak. When i do this trick my engine dies, if the mixture is too weak why are the plugs biscuit coloured. The car pulls well and certainly doesn't run like its to weak, fuel mpg usually around 36-42 (when not much town driving)

Should i just forget this pin trick and leave well alone ??

[MarkyB]

As the plugs are right I wouldn't worry.
Do you lift the pin slowly?

[minor65]

It doesn't seem to matter if pushed up slowly or quickly

[MarkyB]

What kind of biscuit are you judging by? Digestive is about right, Bourbon is too rich.
Rich tea may be a little weak

[minor65]

Digestive biscuit coloured (not a chocolate digestive )

[MarkyB]

That sounds fine, you could look at the amount of wear on the throttle shaft and any splits or leaks on the vacuum advance pipe to account for a little extra air getting in at tick over.

[minor65]

Thanks Mark, I have already checked the vacuum pipe and it's ok. I think I'll just leave well alone. ''If it ain't broke'' etc.

[MarkyB]

It may be worth checking that the vacuum advance itself is working, the diaphragm can split and give a small air leak, not a big deal in itself but the vacuum advance stops working properly which takes the "pep" out of the engine.
The pin method only tests the mixture at tick over, plug colour give a much better idea of the whole rev range.

[bmcecosse]

The piston pin must only be lifted a short distance (about half way) - not pushed right up. But note it only indicates the idling mixture - the plug colour shows the running mixture- which is what matters......

[minor65]

Thanks for that, I'll leave well alone !!