>
> A question about the fast idle on my MGA's carbs. There is a single screw
> which does the very obvious thing: turn the screw down and it pushes a small
> plate which opens the throttle. Turn the screw up and the throttle closes
> until it hits the normal idle stop.
>
> Alas, my screw appears to be screwed. So to speak. I cannot get it screwed
> down enough to make any meaningful difference in the idle, due to a tension
> spring in between the screw head and the plate into which the screw threads.
> The result is that when I use the choke, I get a nice rich fuel mixture, but
> no fast idle, and the car runs very roughly (richly) until it is warm enough
> that I can start backing off the choke. If I do the old manual fast idle
> (foot on the accelerator :-), the engine smooths out nicely, but I get tired
> of doing that. If I back off the choke completely, the car sputters because
> it is cold.
>
> So the question: what's the problem with the screw, and what should the fast
> idle setting be anyway? I suspect the wrong screw is in there and is too
> short or something, but I want to be more sure before I go and mess with it.
>
First off, check the actuating shaft, linkage, and cams for wear.
The 1600 has a funky dual lever arrangement which is not terribly durable.
Especially after 30 years.
Assuming everything's OK, then look at the screw itself. All the original
screws were fillister (sp?) heads. If it has some other kind of head, it's
certainly not original. Fillister screw heads are cylindrical with a rounded
or flat top.
If the screw is too short, due to a worn mechanism, I'd put in a
longer screw. Definitely leave the spring there. It provides some objection
to the screw moving under vibration.
Dave Ambrose
dave@pacdata.com
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