Automatic Chokes

Adjusting Automatic Chokes: A Semi-Universal Approach

Automatic chokes on automotive carburetors are not new technology; they’ve been around for decades. Still, they’re a continuing source of frustration for many enthusiasts. Too often, automotive hobbyists end up removing the automatic choke; or defeating at least some of the functionality of the automatic choke because they don’t know how to make the engine run “right” and still have the automatic features of the choke enabled. If there was one “typical” issue, it would be that the engine starts OK, but almost immediately begins to run really bad—rough and blubbering—so much so that the engine may even stall. The most common mistake I see—about three-quarters of all automatic choke problems—relate to people who adjust the bimetallic choke coil, when they should be adjusting or replacing the vacuum-powered choke pulloff instead. I’m going to repeat that general theme several times—and, yes, it IS that important. But of course there are other problems as well; and I’ll deal with most of them in this article. None of what follows is intended to replace the manufacturer’s instructions. Since “official” procedures and specifications may be difficult to find, though, I’m offering a common-sense “universal” procedure.

The first thing you need to know: It’s going to take longer to read this than to walk out to the driveway, lift the hood, and adjust the damn thing—at least to perform the baseline adjustments. It’s not rocket science; and it can be tricky (and sometimes time-consuming) but it’s not hard. You may need some “special tools” depending on your carburetor, but in general a selection of screwdrivers, a batch of drill bits to gauge distances with, a hand-operated vacuum pump with a vacuum gauge, and some kind of linkage-rod bending tool is about all you’ll need.

The worst part of adjusting the choke is that only baseline adjustments can be made in heated comfort. Baseline adjustments will get...