Spark Plug Colour

[Terry Posma]

Further follow up.

Used a synchroniser to balance the carbs and mucked around with the idle screws but still very rich when adding a bit of throttle.

Changed back to the 14.5mm pumps and that resolved the problem. Seems as if you get extra punch from the longer stroke accelerator pump but at the expense of a whole lot of unburnt fuel. I had quite a plume of smoke coming from the exhaust which has now been eliminated by going smaller.

Last thing is to keep working with the idle srews and idle speed to get a smooth idle. If that does not work I will try some of Keith Franck's idle jets.

[Craven]

Terry
You mention an old set of 31’s; those fitted to a T/C have this throttle plate, note the small air bypass hole in the lower section.
This was added by Lotus to try and overcome the way to advance of the first progression hole in the body. Good luck with the smooth idle, I never achieved it with 31’s.

[Terry Posma]

Yes, I saw the holes and read about the issues.

Will try the Keith Frank idle jets first and if that fails swap the throttle plates for the one that were in the 27s, which have no holes.

[Craven]

Hi,
Before you abandon the 27’s try and remove any broken needle parts from the body holes.
I have run a 1558 cc T/C on 28’s successfully I think 27’s are similar in progression and are close to the original 18’s. although even 18’s are not perfect regard initial idle to 3000 range. You can probably guess I hate 31’s.

[Dellortofan]

Snail STE sychrometer industry standard. If you have access problems rubber ducting from the air box to grille has various bend for it to fit, from a modern van or car. Some times a cardboard tube with gaffer tape may do.
Just put it back before the lady indoors notices...