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MG TD TF 1500 - Jet Levers & Fast Idle Lever

While continuing to investigate issues with my carbs, I noted the following:

1. I have choke, but no fast idle. Never did. I note the front and rear jet levers connected by the jet lever link way down below the carbs to which the choke cable is connected point down to about the 5 o'clock position. This seems normal from what I've seen. When the choke is pulled they only move back to about 5:30 and stop. I know my choke cable is connected with only a tiny bit of slack as it is supposed to be, but they only move to the 5:30 position even if moved by hand. So question #1 is, is this the correct amount of movement?

I also noted the so-called rebuilder of these carbs used a different, very thin, lever for the fast idle lever, and put a spring type spacer there to make up the difference. I also noted the fast idle link (#56 Moss carb page)that connects from the top of the jet lever to the fast idle lever is bent. When I pull the choke, I get good choke but no fast idle, but the fast idle lever does NOT move at all. I can push the fast idle lever plate up a little with my finger, so I know the lever is free to rotate.

I removed the proper fast idle lever from my old spare parts carbs and intend to install it, but my question #2 is, is the fact that the fast idle link is bent why my fast idle lever plate does not move upwards? It would seem like straightening it and making it the proper length would move the upper attaching point upwards, and therefore lower the fast idle plate downwards so perhaps when the fast idle screw is properly reset it will actually move when the choke is pulled.

If I'm way off base on any of this, forgive me, it's 3AM and I should have been in bed hours ago.
L Karpman

Larry, the fast idle lever your referring to sounds like the replacement part that is stamped steel rather than the old brass one. It should work fine as long as it isn't worn out or rusted too badly. The metal rod that actuates the fast idle lever has to be configured to allow the adjustment screw to contact the fast idle lever when the cable is pulled. Since the replacement lever isn't quite as thick as the original, it needs a little longer rod to work properly. If you can straighten yours to get into the proper contact range, that will work fine. Some even make a new one out of coat hangar wire lengthening it a little.
Richard Cameron

The choke cable knob should pull out at least a half an inch or more. Likewise, the end of the cables/levers should move that much. If not, there may not be enough movement to activate the fast idle linkage. The link originally had a bend in it. Richard is right above, suggest installing the original lever first, check total movement, then straighten rod to lengthen if needed. George
George Butz

Thanks guys.

I put the original lever/plate back on the carb and straightened rod, to no avail. I have 3/4" of choke pull at the dash, and levers start moving after 1/8" slack is taken up. Still no movement of the rod at all. The jet lever moves down when the choke is pulled as it is supposed to, but the rod attaching point aft of the jet lever does not move at all to allow movement to pull the fast idle lever end down, and push the fast idle plate upon which the screw rests (with .016 clearance)up.

The lower attaching point of the rod is so close to the pivot point, which does not move, of the jet lever, I'm amazed that the rod could have any effect at all. I know it is supposed to, but I'm stumped.
L Karpman

Could you take a picture of the linkage/rod setup and post?
George Butz

Here you go George. Hope this helps.



L Karpman

And another



L Karpman

The parts I can see are correctly installed. The amount of movement is very small, the rod is pulled down, which rocks the lever up into the adjustment screw. Could there be too much slack/wear? The rod is too long? The adjustment screw needs to be turned in? Has to be one of those things. After seeing the picture - the rod pulls, not pushes, so the advise to straighten /lengthen rod wrong, needs to be shorter. Sorry about that. George
George Butz

Yes George, I made the rod smaller earlier and reinstalled.

I found the issue I believe! I was only able to pull my choke out 3/4". Even pulling/pushing the link between the jet levers by hand only yielded a move from 5 o'clock to 5:30 to a hard stop. I checked to see if there was binding/blockage somewhere, and sure enough the rear carb jet lever was not aligned with the rear link preventing it from passing through the opening. I pushed the lever inward and it now passes through allowing a full 1 1/2" choke pull (with the first 1/8" slack). Also the fast idle lever moves!When I have another hand I'll have them pull the choke and see what adjustment is need for the fast idle.

Thanks for all the help, and I'll report back the results.
L Karpman

Well in trying to set up the fast idle properly, I need some info. My choke knob has a total travel of 1 3/4". The fast idle lever does not contact the screw and move upward until the choke is pulled at least 1 1/4" or to the tip of the first notch visible when pulled. I don't know if this is excessive or not. The only info I have on setting the fast idle screw only says,

"To adjust the slow running control, turn the adjusting screw until there is about .016 in. clearance between the screw tip and the rocking lever. The purpose of the small gap is to make sure the fast idle mechanism can’t hold the throttle slightly open even when the knob is in the full off position."

It would seem that the position of the fast idle lever, plate, and screw tip are not a factor, as regardless of position, the plate does not move upward until I reach 1 1/4 travel on the choke knob.

Can anyone advise if this is normal or abnormal, and are there instructions available for setting the fast idle properly? I've searched the archives with little success.
L Karpman

I think there is a lot of slack and play in the linkage/lever. I suggest turning the adjustment screw down to eliminate all play or slack in the linkage. At this point any movement in the jet lever should move and increase the idle, then back off a half a turn or so.
George Butz

George: There is only 1/8 inch slack in the linkage before the linkage moves, but the fast idle lever doesn't move until I pull about 1 1/4". The tip of the fast idle screw is only .016 from the lever plate. Is this excessive?
L Karpman

Forget about measurements. With engine running and choke in, tighten the fast idle screw until the engine actually speeds up a touch, then back it off until idle normal. This should create a fractional amount of slack and it should work fine. If not, I have no idea. Anyone else have any ideas or suggestions? George
George Butz

George: I tried that to no avail. It really boils down to "when" the fast idle plate moves. Moving the jet lever linkages by hand via the bottom connecting link, I have to get to about 3/32 - 1/8" of jet showing before the fast idle linkage moves upward. I think there is too much free play on the front carb jet lever pivot point to move the fast idle rod earlier. That's all I can come up with for now. I'm open to any and all suggestions. Thanks for the help.
L Karpman

Just looked at mine- at about the same jet movement distance, the link lever/screw are in firm contact and the throttle begins to open. Maybe you could take the air cleaner manifold off and with a helper observe, should be apparent where the problem is (worn/sloppy parts, etc.)Make sure you have the correct lever to carb bolt with the smooth pivot surface, and not something generic. There is not much movement at all-when working correctly, it just cracks the throttle a bit, not like an old automatic choke car that would really rev. George
George Butz

Check all of the pivot pins in the linkage for excessive wear and replace with new ones to tighten up any slop in the mechanism.
Richard Cameron

George: When you say, "at about the same jet movement distance," are you saying your lever does not move until 3/32-1/8" of jet showing also?

If I take the air cleaner manifold off again, what am I looking for specifically that I can't see with it on?

I do have the correct bolt and the correct lever.

Right now, I have to pull the choke out (moving the jets down 3/32 - 1/8") to get the lever to move, and all this does is make the car want to stall from too much choke. Guess I just want the lever to move with a lot less choke.
L Karpman

"Check all of the pivot pins in the linkage for excessive wear and replace with new ones to tighten up any slop in the mechanism."

Richard: That is my main suspect right now. I have some spare pivot bolts on my old car linkages, but in case they are worn also, where can they be purchased? I don't see them listed in Moss carb diagram page.
L Karpman

I purchased some from Moss. Give them a call. They were inexpensive.

Joe
JWP Policastro

Thank you sir! I found them in the Moss diagram #59.
L Karpman

Send me an email with your address and I'll send you some--- I bought too many from McMaster Carr.
Richard Cameron

Sorry--- here's my email address
Richard Cameron

Email sent. Thanks!

A friend stopped by today and we carefully watched the fast idle lever and plate move. It actually moved "down" a bit before moving up, which tells us that the linkage is very sloppy, and possibly the reason for so much pull needed on the choke to move it upwards. At least that's tonight's theory :-)
L Karpman

Larry, I had poor lighting and no helper to hold the bonnet open when I looked, but at the distance mentioned above the idle began to increase, could not see initiation of lever movement, but likely as soon as the jet link moved at all. I think you are on the right track with sloppy linkage and hopefully the new pins will help. Removal of air manifold was just for visibility's sake. George
George Butz

Thanks again George. I've got some new pivot pins on the way. Hopefully that will solve the issue. Just out of curiosity, any idea how much RPM rise would be considered normal for fast idle before too much pull chokes the engine out?
L Karpman

Anybody have a "ballpark" answer my last question?
L Karpman

Larry, I can easily get over 2,000 rpm from the choke knob. By that time I'm pushing the knob in. Bud
Bud Krueger

Thanks Bud. Just needed a general point of reference for when I install new clevis pins and hopefully get this fast idle lever working as it should.
L Karpman

This thread was discussed between 16/09/2014 and 21/09/2014

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