Choke adjustment

[Al Schober]

At the end of last season, I noticed that the engine was getting hard to start. Suspected at the time that the choke wasn't closing properly, and added it to 'the list'.
Today I got to it, and yes the choke wasn't closing fully. The wire in the cable looked mangled, and it turns out the wire attachment gizmo wasn't pivoting properly in the choke arm. I was unable to free it up onboard, so just swapped out the arm & gizmo for one from a spare carb. Spent some time straightening out the wire, and got it all working. Choke now comes on (and off) as desired, and things are good.
As a side issue, has anyone else noticed that the attachment for the choke cable jacket seems too short? The wire is always bent away from the pivot - sometimes a little, sometimes a lot. Seems to me that if the arm holding the cable jacket were a bit longer, bending of the wire would be a lot less - ideally a little bit one way, a little bit the other way.

[hanleyclifford]

The problem is one of converting linear motion to angular or rotational motion. Greater minds than mine are thrashing this around; I'm open to suggestions. http://functionspace.com/topic/3704/...and-vice-versa

[JOHN COOKSON]

As a side issue, has anyone else noticed that the attachment for the choke cable jacket seems too short? The wire is always bent away from the pivot - sometimes a little, sometimes a lot. Seems to me that if the arm holding the cable jacket were a bit longer, bending of the wire would be a lot less - ideally a little bit one way, a little bit the other way.

Yes I did notice. I set the hold down gismo so it was lined up as best as I could get it when the choke was 1\2 open\closed. Maybe the "great minds" can tell me if this is the correct procedure. Best I could come up with.
I also found out that the outer cable will stay in place better if it protrudes just a bit through the Mickey Mouse hold down clamp.

TRUE GRIT

[hanleyclifford]

As I see it the problem is that the "hold down gizmo" is too close the point where linear becomes rotational. Here is an illustration of the concept:

[ndutton]

What is the problem?

Has there ever been a choke function issue due to the fixed mount? I set mine the same as John, aligned at the mid point so the cable core deflection maxes out at only 50% either way.

I dunno, 40,000 Atomic 4's, 20,000 still in service, choke mount design has been that way for 67 years and the concern is what??

[hanleyclifford]

Has there ever been a choke function issue due to the fixed mount? I set mine the same as John, aligned at the mid point so the cable core deflection maxes out at only 50% either way.

I dunno, 40,000 Atomic 4's, 20,000 still in service, choke mount design has been that way for 67 years and the concern is what??

There is always room for improvement and engineering advances by stages, sometimes small and seemingly insignificant.

[ndutton]

There is always room for improvement and engineering advances by stages, sometimes small and seemingly insignificant.

Then go for it. Should be interesting to see your improved version.

[JOHN COOKSON]

Once I set the choke cable hold down how thought was best I scribed a line on the hold down and the carburetor with a diamond tip pencil so I could line it up again with out readjusting on the next (and the next, and the next.........!!!) carburetor rebuild.
It was hard for me to visualize the correct position for hold down when the carburetor was off the engine and disassembled because of the angle of the choke cable comes to the carburetor.

TRUE GRIT

[edwardc]

As a side issue, has anyone else noticed that the attachment for the choke cable jacket seems too short? The wire is always bent away from the pivot - sometimes a little, sometimes a lot.

I too had an issue with this some years ago. Choke either wouldn't open all the way or close all the way, depending on where I clamped the cable sheath. It looked to me that the barrel clamp on the choke arm sholud be free to rotate but wasn't. This caused flexing of the stiff inner cable at the clamp end in addition to the flexing at the jacket attachment point. The combination was just too much to overcome.

I solved the problem by taking the choke cable and bending a "U" shaped hook in the inner wire, and hooking this over the barrel clamp's screw instead of clamping it. This eliminated the stiff flexing at the barrel clamp end, and the choke's return spring kept the choke arm engaged in the hook. An added bonus was that it makes carb reassembly that much easier, as I always had the most trouble getting the choke cable aligned and clamped properly due to poor access.

I dunno, 40,000 Atomic 4's, 20,000 still in service, choke mount design has been that way for 67 years and the concern is what??

I think the potential issue comes from the particular choke cable used rather than the mount design. I've noted a wide variation in choke cables used, with differences in both jacket and core wire construction.

[Dave Neptune]

My choke "assembly" does not flex as both ends pivot.

Dave Neptune

[HOTFLASH]

"U" in choke cable

Hey Ed,

Could you post a pic of what you described in #9: the "U" in the choke cable in the barrel clamp? And thanks.

Mary

[ndutton]

I too had an issue with this some years ago. Choke either wouldn't open all the way or close all the way, depending on where I clamped the cable sheath. It looked to me that the barrel clamp on the choke arm should be free to rotate but wasn't

The inner cable attachments on all three of my carburetors swivel and I hafta tell ya, the choke works fine on all of them, always has.

And FYI for all, the accurate term for the cable under discussion is Bowden Cable.

[roadnsky]

Mine swivels too. Here are a couple pics.

Hey Thatch, wanna say anything here?

[Dave Neptune]

My choke arm is the stock pivot, I did cobble a swivel mount for the sheath end myself. Works like a charm and the cable moves a bit easier. I did this as my old stock cable in the cockpit was about 12 feet long. After redoing my engine box about 25 years ago I eliminated the choke from the cockpit and mounted on the control panel on the box itself at the nav station. I always "cold start" the engine before taking off from inside using my remote permanently mounted "starter only" button on the inside of the engine box.

Sorry no pics on this machine. I have posted pics on this site prior, just don't know how to retrieve or find.

Dave Neptune

[thatch]

Okay Jerry

As Jerry is aware, I am in the process of installing a new gauge panel and have decided to use an electric choke rather than run a 13' Bowden cable. Recently, while cold starting my engine, I have been simulating the action of an electric choke and it worked well enough that I am going to take the plunge. In the future, If I feel the need to install a manual choke cable, I will be using a Morse style 33 series instead of the commonly used Bowden type.
Tom