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MG TD TF 1500 - Choke fix - no more clothespins

I got tired of using clothespins and decided to fix the choke cable.

The cable has a series of notches in the brass end fitting, and a tiny key that fits in a transverse slot cut into the outer housing. The key is kept in the slot by a spring steel cylinder that fits over it. The key drops into the notches and the spring holds it in place. Turning the knob forces the key onto the un-notched part of the brass fitting, pushes the key against the spring, and allows the inside cable to retract.

The notches get rounded and the key gets worn; the archives recommend replacing the key (which is very difficult to make as it is so small), and rejuvenating the notches. In my case, I noticed that the key was not terribly worn, but there seemed to be a lot of play between the inner and outer cable.


J Barry

Turning the cable over, I noticed two punch marks, and figured this might be used to take up the cable play. I used an old screwdriver for a punch and gave each mark a couple of whacks.

I'm posting this because I did not see this particular aspect of the cable design in the archives.

J Barry

Sure enough, the cable now works beautifully. I also dressed the notches.

J Barry

Good advice - the mechanism is simple once you realise there should be a small half moon in the slot under the sprung collar. However after making a new half moon for my choke control the thing still didn't work properly. I sorted this out by releasing the inner cable at the carb and twisting it so the notches on the shaft were sprung into contact with the half moon.

Jan T
J Targosz

Jan,
The punches form a ridge that fits into the "t" geometry of the underside of brass end fitting. That and the sprung key should keep the inner and outer cables oriented properly.

Jim
J Barry

J Barry. Good tip. Thanks for this.

But do you really need to use the choke in HI? :-)
Christopher Couper

Any advice on getting the large nut, behind the dashe, off the back of the outer tube/cable?

Jim B.
JA Benjamin

Mauna Kea

James Neel

Jim B: I don't have much advice for getting the nut off. Disconnect the battery, use a good drop light, and prepare to assume an impossible position.

Chris - my car is in San Diego; it's a long distance thing that is often frustrating. It's actually warmer there right now, and yes, a choke is still part of the start-up.

James - if I bring the car over, Mauna Kea is definitely one of the drives on the list.

Jim

J Barry

In one of my old Morris Minor work shop manuals there is a drawing of how to preload the inner cable with a twist where it attaches to the carb linkage, so that the notches and detents on the sleeve near the knob work, effectively holding the cable in about 3/16th inch increments when pulled out. Not sure if the latest T series cables are designed the same way or not but the Moss cable I bought a year or so ago was set up this way. It is a stranded wire inner cable that, being more flexible, works so much better than the stiff solid wire one I lived with for many decades.
John Quilter (TD8986)

The PO of my car replaced the choke cable and used a non-locking type which didn't hold either. As a quick fix, I pulled the inner solid wire out and made a gentle bend about every 6 inches in opposite directions. When I replaced it into the outer jacket there was enough friction to hold it in position.
Mike
TD15250
Mike I

Hi Jim,

The notches and half moon will keep the control locked but only if the wire to the carb is set with the correct twist. Otherwise it will turn the shaft and the half moon will become detached from the notches. On my TF as I pull the knob out I hear clicks. I cannot simply push it in but have to turn it 1/4 turn clockwise and can then push it in one notch at a time.

A problem I do have though, pull the knob out two notches and the idle goes up to just over 1000. Pull it out any more and the revs increase to nearly 2000. This hasn't been a problem during the summer when one/two notches was all that was needed at start up now that winter is here three or four notches are required. I realise the problem is at the carb end of the control but it is too cold to do anything about it at the moment.

Jan
J Targosz

Jan,

Sounds like your TF cable is almost working properly. I think those punches are a key element. Too deep and the cable may not turn enough for proper release. Too shallow and the fittings will be loose. I struggle with the carbs too... maybe your fast idle screw needs to be backed off?

Jim
J Barry

I, too took out the choke cable from my TF to lube and clean it up. Upon reassembly and putting on the spring clip, the little half moon piece went flying, and disappeared under one of my tall shelf units, in the garage.
I proceeded to make a new one with some sheet metal, and got it together It worked well and I re-installed it. Just two more tries and the half moon dislodged again. Too much work to get it off again and so I'm living with it. Next time I will use a piece of a hack saw blade to make a harder widget thing.
I think this is the smallest part in an MG.
Cheers, Byron.
JB Warwick

I used a hack saw blade to test the system. The thickness is perfect. But the piece is so tiny, I have no idea how one would cut it to shape.
J Barry

Grind it, don't cut it.
Lew Palmer

Quote
" I used a hack saw blade to test the system. The thickness is perfect. But the piece is so tiny, I have no idea how one would cut it to shape."
End Quote.

If you are talking about the key.

Start with a rod the correct diameter. Brass is good.

Sans mill or lathe clamp in vise, file a step 1/2 way through. File edges,

Cut off to correct thickness or a bit large with hacksaw.
If needed, run back and forth on a smooth file to control thickness.

Jim B.

JA Benjamin

Lew nailed it. Grind the hacksaw blade. It will last until you lose it. :-)
Christopher Couper

Is brass not to soft for the key?
Will it not wear quickly?
John van den Boorn

This thread was discussed between 29/11/2017 and 03/04/2018

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