Engine won't idle

[barry young]

I've had an intermittant problem with my 1957 saloon not idling unless the choke is out or I keep the foot on the accelerator. By the colour of the plugs, the mixture is fine. It runs fine at any speed. New coil, Distributer Doctor points and condenser, new plug leads recently. Is it possible there's some muck blocking the idle jet in the carb? Is there an idle jet? Any ideas much appreciated!

[philthehill]

There is no idle jet in a H2/HS2 carb, just the main jet.

[barry young]

Thanks for that. Could a partially blocked main jet or some other carb problem be causing this?

Forgot to mention I've checked tightness of manifold bolts in case it was sucking in air.

[Monty-4]

If the mixture is generally fine and it's intermittent I'd check the carb piston is sliding up and down smoothly and there is oil in the dashpot.

[barry young]

Ah, thanks, good suggestion. I wouldnt have thought of that. In fact, I can't remember the last time I checked the dash pot for oil.

[barry young]

Well, that was satisfying. Cleaned off some black marks inside the piston chamber and some brown glazing. Carefully polished off some chalky residue at the base of the needle and now it seems to be running fine. Also, I don't need to pull the choke cable out as far as it will go to start it in the morning.

[myoldjalopy]

Result! Nice easy fix too - we like them!