carburettor adjustment

[ethel]

Hi again,

Spent this afternoon checking the carbs over and hopefully tomorrow will get to adjusting the mixture and idle. I found a very split diaphragm and a needle that was reluctant to adjust, so freed off the needle and fitted a new diaphragm. As a start point I wound the needles back about 2 full turns from their fully down position - is this about right?

Also as the air cleaner is removed, the small tube that goes to the temperature valve in the bottom of the air cleaner assy from the carb pedestal is disconnected, should I try to close this off so it won't suck extra air in (bypassing the carbs), or is it ok to leave it open?

Thanks,

John.

[V Mad]

imported post

Close off the pipe as the air sucked in will weaken the mixture slightly.

[steve]

imported post

john



did the same job last weekend, found a diaphram split and needle sticking, freed the needle replaced diaphram adjusted base off needle level with base of piston then turned up one and half turns clockwise, refitted and even with just that initial setting car was far better than before



steve

[Guest]

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Hiya John, I agree with Steve, just to add a bit, you need to take the pistons out and setboth needles with there shoulders flush with the piston, they MUST be exactly the same, then follow Steve's advice.Enjoy. Martin.

[peter f]

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Hi John,
I got mine spot on using Martin's suggestion for setting the needles. I also viewed a previous thread for balancing the air intakes, by using a rizla fag paper so it just slipped under the butterflies at either side - with the linkage disconnected. Crude but very effective in my case.
I bought a balancing gauge off fleabay, where the air inlets suck a ball up a graduated scale in the gauge, but could not get a consistent reading, so resorted to rizla.
hope you sort it,
Peter

[ethel]

imported post

Martin Stevenson wrote:

Hiya John, I agree with Steve, just to add a bit, you need to take the pistons out and setboth needles with there shoulders flush with the piston, they MUST be exactly the same, then follow Steve's advice.Enjoy. Martin.

Thanks everyone, setting it from the flush position sounds better than trying to judge when the needle started moving from its lowest position.

When the car had its last MoT (a few years ago), the CO reading was a bit high (it's a '76 so it does matter to the test - in theory) so that's what I'm trying to correct, I've read that the idle trim screw (on the side of the carb near the temperature compensator) can have a good effect on the CO, does anyone know what the 'default' setting of this screw should be - at present mine are set 2 turns out from the point that the spring on the screw binds up.

John.

[Guest]

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I've had two expert opinions on that screw, one says closed then back 3/4rs, the other says screwed in, I've tried both and no difference, I believe they were a concession to the American market and in reality serve no purpose in our cars. Martin.