63 AFB - sticking choke pulloff

[Joseph S.]

On both my 63 AFB carbs the choke pull off piston will stick in the housing bore and prevent the choke from setting if the cars sit more than a week or so. A little hand coaxing unsticks the piston but years of trying various lubricants and reworking hasn't improved the situation much. Any fixes or source for new piston. Thanks

[Duke W.]

Re: 63 AFB - sticking choke pulloff

That's a common AFB problem. At the most you should lubricate the bore with nothing more than a film of WD-40.

It may just be a maintenance issue - remove the choke housing periodically to clean the bore and piston. It's not that hard, but you will need a supply of small O-rings that seal the choke housing vacuum passage to the carb. main body.

Verify that the internal hot air tube in the manifold is not rusted through. If it is, the piston/bore will rapidly become dirty and sticky.

I also recommend a cellulose air filter other than judging as the oil in the urethane filter will work it's way into the vacuum break and cause it to become sticky. (Also, the urethane filter has poor particle filtration compared to a modern cellulose filter.)

Check the bore and piston for galling and dress down any high spots so the piston moves freely in the bore. I'm not sure of a source for new choke housings or pistons, but you should contact the various carb rebuilders.

Also, with the choke valve drive link disconnected, verify that the valve moves freely through its full travel without sticking of binding.

Duke

[Frank D.]

Re: 63 AFB - sticking choke pulloff

All of Duke's sage advice is spot on as usual. I am very reluctant to do anything abrasive to that choke bore though....its a pretty finicky setup.
One trick that never seems to fail (at least on Carter WCFBs) is to take the plug out of the bottom of the choke piston cylinder; get a small gun cleaning brass brush and some Hoppe's Number 9 solvent and scrub the snot out of that baby just like it was a rifle bore. This removes all of the carbonization.

Doesn't hurt to hit the piston with the same procedure.

[Stuart F.]

Re: 63 AFB - sticking choke pulloff

I believe in my over 50 years of experience with four different AFBs on my 63 L-76, nothing ever worked for long to combat the white corrosion problem as long as I used the original hot air tube source for heat. In the process to combat heat soak and percolation, I threw a lot of changes at my carb including an electric choke. I no longer have a problem, even still using the standard choke pull off mechanism. Granted it ain't NCRS correct, but I like to drive my car-not just show it. And, I'm getting too old to tinker much in central Florida heat. My electric choke uses a thermal sensor (not like Edelbrocks) which senses the manifold heat and adjusts the choke according to the engine's needs based on engine temperature. It works super.

Stu Fox

[Frank D.]

Re: 63 AFB - sticking choke pulloff

Why bother even having it operational in Central Florida ? I just wired mine open...problem solved...

[Stuart F.]

Re: 63 AFB - sticking choke pulloff

Seems to me we are entering the "cool" season, even here in Florida. It's nice to go out on a cool Sunday morning, kick the throttle to set the choke, and have the engine start right up and high idle with no stumbles or hesitations reaching the first stop sign. The engine speed steps down nicely and off you drive - just like up north in the cool spring or fall mornings. You shouldn't have to sit in your garage for ten minutes goosing the throttle to impress the neighbors until your engine is warmed enough not to kill at the first stop sign.

I forgot to mention; my electric choke uses a loop on the end of the bi-metallic coil to capture the tang on the choke pull off. This way, it not only pulls the choke closed when cold, but assists the choke pull off by pushing the choke open as the engine warms up (2 way action). It's a sweet device.

Stop by and say hello at the next show if we meet and I'll show you how it works.

Stu Fox

[Frank D.]

Re: 63 AFB - sticking choke pulloff

Wow - I don't have any of those cold start problems with my WCFBs in central Florida. On the '61 or '63; I might get a bit of a lean stumble as I exit the garage with the '61, but I 'feather' the gas just that once and I'm off with no issues. The '63 just hums along from the git-go...

In any event I hope the OP gets his choke problem solved.

[Timothy B.]

Re: 63 AFB - sticking choke pulloff

I used some powdered graphite on the piston and cylinder.

[Thomas B.]

Re: 63 AFB - sticking choke pulloff

The choke piston on my AFB is not allowing the choke butterfly to close completely. The piston and bore a are not gunked up but the piston binds or sticks at the top of it's travel. Not able to remove the piston from the bore easily. Should it pull out of the bore after removing the screw holding the piston inner lever to the outer lever?

[Edward J.]

[Thomas B.]

Re: 63 AFB - sticking choke pulloff

I was able to get the piston out. Had to pry gently on the inner lever arm with a small screwdriver to do so. Polished up the piston enough to provide free travel in the bore. The bore didn't require any work. Choke now works properly. Thanks