Thread: SU Carbs Installed now High Idle

SU carbs have been installed see - Carbs & Manifold

Now it runs with a fast / high idle. I've checked throttle linkages, accelerator cable and idle screw and they all seem ok. I topped up the pots when I installed them.

I did use Stromberg gaskets when installing the SU because that's all I had at the time but they all seem fair standard patterns anyway.

Any ideas what else I should be looking for?

Also, anyone have a clue how to hook the choke cable up?

TIA

Stu

Have you done a "Balance".

You will need to balance airflow and mixture.

Use a cigarette paper to set the butterflies and the dual linkages. Everything loose!

Release, unwind the the idle screws till the butterflies bottom out, adjust the idle screws till they just snag the cigarette paper. Then lock up the linkages; check to see that both butterflies are still bottomed and the idle screws still snag the cigarette paper. Play till you get it right!

Then adjust both idle screws in an equal amount and start the vehicle. adjust both sides equally until the idle speed is as slow as the engine will run - just cuts out.

Next increase idle both sides till the engine just runs.

Find the lifting button under each SU piston and gently lift each side in turn and together. If the mixture is correct the engine will speed up then stall. If too rich it will just increase in speed, if to lean it will stall.

Ideally one should use an "air" balancing device after the carbies are mechanically set for airflow balance and something like a "colour tune" for mixture balance.

You need to be a bit/little/trifle lean here!

Once its all done test drive. Flat spotting indicates that mixture is a trifle lean. Gradually increase richness a flat at a time each side till flat spot goes.

This is why one uses solexes They stay tuned!

Used to have to do a 3/4 cam 1310 Cooper S every week end.....much later I went berserk an installed 2" SUs onto a RRC 4.2. You have a Choke cable......Awwww!

Should be a lever that pulls the mixture tube/nut down only use on one carb. Later SUs had an enriching device that is was a PITA never ever really worked properly after the cars were out of warranty. Too rich or too lean or wouldn't shut off.

Cheers

RF