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MG TD TF 1500 - TD Carb linkage

I need some help with the fast idle linkage on my stock '53 TD carbs. It looks like I'm missing the fast idle lever and linkage that activates it. I think I can get the needed parts from Moss, but I'm not totally sure of the configuration or exactly what I'm missing. The carbs have been messed with by many past owners and has never worked since I owned the car. The fast idle lever with the adjusting screw is now located near the rear carb and looking at the diagrams this may be incorrect. Are there any good photos on the net showing the detail of this setup or can someone please send me a good photo so I can get this working properly? Another question on the same subject, when I pull the choke cable for enrichment on cold startups I have to hold the knob out manually, do I have the correct cable, or should it be of the locking type. Is it possible that once I have the correct fast idle linkage installed it will stay on by itself?
A.G. Gruskos

Does this help A.G.

The link is on the front carb on my late TD.
Simple bent rod with split pins holding it
Moves a rock leaver that engages with an adjustment screw - just by the slow idle screw.

When you push the choke back in - the bottom jet leavers move forward and up to push the jets back up to the bridge. It will also move the fast idle leaver so that it has no more effect.

To hold the choke leaver out after you have pulled it just turn the knob through 45 degrees and it should lock in place.
To remove the choke - simply twist back and push in.

Rod

R. D. Jones

Rod,
Thanks it did help. I know what I have to order now. I think I just have a cheap reproduction choke cable installed that doesn't turn to lock like it should. I'll have to order the correct cable too.
A.G. Gruskos

Do you have 1-1/4" carbs or 1-1/2"? I don't remember that TDs came with fast idle on the 1-1/4" carbs - you probably have MGA carbs.

Tom
t lange

Tom, The early TD came with the same configuration, and they have the 1-1/4" carbs. The fast idle is there, and when set up as per the WSM... is just about useless.. :-) My car has the exact same set up and is Sept. '50.
... CR
C.R. Tyrell

Tom, the 'fast idle' is probably the action from the front jet lever when the choke is pulled out. I think the 1-1/4" and 1-1/2" use the same mechanism. Don't they? The lever and link are the same. Bud
Bud Krueger

A.G.
When you but a new choke cable.

It will work - only in the reverse way of the original cable.

This is because the original knob rod part had a ratchet cut in it. With the original choke cable on My TD you would just pull the knob strait out and the ratchet would hold it at the setting you had made. To return the choke you would twist the knob to disengage the ratchet and push it back home.

With the new modern [cheaper made] choke cables now on the market. There is no ratchet - but a v grove in the knob rod part.
To engage this type of choke. You pull out the choke knob and twist it to cause friction from the small pawl against the choke rod by virtue of the circular spring.
To remove the choke simply twist the knob back to relieve the the pawl pressure on the rod and push home.

Both ways work fine.
Hope this explains it
Rod

R. D. Jones

I just took a look at my cable and it looks like the reproduction one in the diagram, but it doesn't work as it should. It was purchased from Moss years ago. Hopefully their quality control is better now.
A.G. Gruskos

Rod's drawing makes it very clear. Here's a pic of my original choke prior to restoration showing all the components. The tiny item at the top is the key & the steps or stops cut into the shaft are just visible. The housing for the key or pawl can be seen at the bottom right. On assembly the sleeve slides over the opening to secure the key which is often MIA. Cheers
Peter TD 5801

P Hehir

A.G.

Just check to see if the circular spring clip and pawl are in place.

If it is a repro cable it should still work OK.

Sometimes stuff happens and bits go missing :)

Rod

nice original shot Peter :)

R. D. Jones

Rod,
Thanks for the photos. It explains a lot. I have the spring tensioner, but the pawl must be missing. its hard to get a good look at it when its installed. It must have come that way because it never worked as designed.
A.G. Gruskos

C R Tyrell: Yes I agree the fast idle feature on the TD carbs is virtually useless in my opinion. Pull the choke out and you immediately drop the jets. My 1960 Morris Minor carb linkage works far better, the first two notches on the choke knob give a two step fast idle then further pulling the knob get enrichment. Never could figure out why the MG system did not work as well.
John Quilter (TD8986)

I don't see why the fast idle does not work on your carbs?
There is an adjusting screw that will set the fast idle faster or slower.
The rocker arm, operated by the small rod installed in the center hole of the forward Jet Leaver which moves down when the choke is pulled - moves up to push on the fast idle screw.
That turns the throttle shaft to open the butterfly port and raises the RPM's
You can adjust how much you want it to increase within reason.
Adjusted too high and the throttle will stay open and fast idle with the choke in. You don't want that.

Back off the fast idle screw - Use the slow idle screw to set the slow running with the engine warm to say 800 RPM - Then adjusted the fast idle screw to just grip a piece of paper when the choke is fully in. This will give you the maximum fast idle - You can back it off if it is too high when the choke is pulled.

I think it works just fine? Cheap and simple :)

Your throttle shaft bushings do need to be in good condition - no slop - also the pins in the carb linkage should not have a lot of slop in either.
The movement is not large and you could lose a lot of the lift if there is a lot of slack in the mechanics.

Remove the air cleaner and the carb piston and look at the butterflies. You will see if they move or not. and if not - can work out where the movement is being lost.
Just my 2c worth. ļ
Rod.
R. D. Jones

The fast idle lever is on the front carb both 1 1/4 & 1 1/2 inch carbs, as Rod noted all slop or free play must be removed from linkage, shorten the link between the 2 carbs as much as possible.
Len Fanelli

The fast idle arrangement works very well if correctly adjusted. Pushing the pedal down a bit and holding before pulling the choke takes the load off of the lever and makes pulling much easier. George
George Butz

This thread was discussed between 08/06/2015 and 17/06/2015

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