MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - Throttle Cable Binding

PO installed throttle cable is binding.

The cable is basic braided wire hooked to the pedal arm, goes up through the hole/short tube in the upper footwell panel, makes a hard turn and feeds through a fitting set into a carb bracket, then goes to the throttle arm. Standard stuff I would think, but the cable is binding where it exits the footwell and enters the bracket fitting. It's actually cutting into the metal owing to the acute angles. There is no external sheath.

I think the sheath would help greatly in reducing the binding and stopping the cutting. I know others have used various auto, tractor, lawn mower, bicycle brake/gear cable, but how is the sheath anchored to the footwell and fitting? Do I need to find very thin sheathed cable or drill out the footwell exit point and fitting?

I've attached a pic. Any hints, tips, suggestions would be greatly appreciated.

Cheers,

Glen


G. D. Phillips

Glen. The pictures are not great. I am assuming that you have a later model car which has the original Z-S carb replaced with a Weber DGV series.

When this conversion is made, the original cable sheath is used with either the original stranded wire cable used or a section of bicycle handbrake/shifter cable used. The bike cable fits well inside the original cable sheath.

But, there may be a little "creative engineering" required when doing this. I have the DGV installed in three MGBs and found it to be a fairly simple conversion. But, I had a well working example to examine before I did the first conversion myself.

Post a couple more photos, including one that shows the carb, intake manifold, and existing carb linkage and we will have a better idea of what is happening and can provide more directed advise.

Les
Les Bengtson

Oops, my bad. The car is a US spec '72 midget with a PO installed Weber DGV on a 1275cc engine. The pedal and arm are stock. The existing cable is a retro-fit and there is no outer sheath. The stranded wire cable is actually starting to saw notches at the footwell exit point (just to the left of the bolt in the top section of the photo) and the entry point to the carb bracket fitting (bottom of photo). This is due to the sharp angles at both points. I've included a drawing as viewed from the front of the car. The upper drawing shows the existing setup, but the angle of entry into the carb bracket fitting is sharper than I've drawn it.

Neither of the exit/entry points have a sufficient diameter to pass the cable AND sheath through them. I would like to add sheathed cable to smooth the curve of the cable as it comes up out of the footwell and enters the bracket fitting. I can't figure out how to anchor the sheath at the exit/entry points. My plan is shown in the lower drawing. OTOH, I may be completely off in my thinking; suggestions?


G. D. Phillips

Here's another image (taken in 2007 during a cleaning, derusting, and painting). You can see how the bare cable exits the footwell roof and takes a sharp angle to the cable bracket on the carb. What I'm aiming for is having the cable exit the footwell, go up for an inch or so, then start a gentle curve to the carb cable bracket.

At the moment, I'm out of altitude, airspeed, and ideas...

Glen


G. D. Phillips

Not sure what your problem is, the footwell tube should take a cable outer without any problems, that's what it's designed to do. A simple bike outer cable should fit easily. Are you sure it's not full of paint? Run a suitable drill into it to clear the crud, but make sure you dont go right through!!!
At the carb end, I would drill into the metal/plastic tube enough to take the cable outer, again don't drill right through, about 5mm in is enough. Or remove the metal tube from the plastic and replace with a threaded metal bike cable adjuster.
Cheers John
JOHN HALL & JULIE ROBERTS

Glen. Again, a photo of the carb and intake manifold, taken from above, would be of significant value. It is hard to tell, exactly, from the photos you have provided, but I believe that the carb may have been installed incorrectly. This is based on the perceived location of the bell crank.

As John notes, the receptacle on the shelf of the firewall should accept one end of the outer cable sheath. The white plastic piece that the cable slides through on its way to the bell crank is not something I have seen before as part of the Weber kit. Normally, the Z-S carb throttle cable sheath is used with this conversion.

But, if you a 72 vehicle, the SU carbs were standard and I would give very serious consideration to restoring the car to original conformation.

Les
Les Bengtson

Hmm, this is getting way more complicated than it should be. Dang PO imagineering...

John: I take it that the footwell tube does not have a constant inner diameter; that is why I'm not to drill completely through it? I'll check it out for paint and dirt, but at this point its diameter is too small to pass the cable, its outer sheath, and the metal ferrule at the end into the tube.

Les: The white plastic disk is simply a threaded retainer and is threaded onto the fitting in the carb cable bracket. The fitting interior diameter is constant and also too small to run the cable sheath into it. Perhaps changing the fitting might be better than drilling through it?

The fitting aligns the cable with the linear action of the throttle bellcrank across the back of the carb. The choke cable runs along the inner side next to the valve cover. Not sure what you mean by 'installed incorrectly'. I'll pull the air cleaner and get a top view pic this afternoon after I take care of my honey-dos.

I'm ok with the Weber, it runs well. SUs are not in the budget. Gotta eat y'know...

Cheers,

Glen
G. D. Phillips

Glen.. I just replaced one on an MGB. I went to Western auto and bought a repair cable for a bicycle.. Use a little imagination and you will have it working in no time at all. . The ball on the end of the new cable insert is fitted to the slot on the pedal and then cotter pinned.
Sandy
Sandy Sanders

Glen,

I think the plastic/metal fitting on your carb is on backwards. Is the metal piece threaded into the plastic piece? I think that is the adjustment. Take it off and see if you can turn it around so that it is pointed the other direction. Then the threaded center piece will probably accept the outer cable, and that threaded portion is the slack adjuster. Like others said, the other end should accept the outer cable.

Charley
C R Huff

this seems to be a clear case of over thinking!

just buy a new inner and outer cable (anny bicycle one will do)
and it wil all become clear
and it won't cost that mutch
Onno Könemann

GD.

Yes you do want the sheathing to go from the carb bracket to the footwell hole from the footwell to the pedal,,,its bare

you want a high end cable from a bike shop with silicon reinforced sleave...Id get 2 made, one as a back up....you can use a cheap bike cable ...it will last a year but not much longer.

Prop
Prop

I agree with Onno- just get a proper throttle cable (inner and outer)and fit that. To be honest, I'm surprised an unsheathed cable works at all. You might as well use a peice of string! The outer sheath directs the inner cable in a smooth curve but without it the cable will just bend as it comes out of the footwell and bind up.
Chris H (1970 Midget 1275)

Most modern bike cables (outers) are now quite thin, so should easily go into the footwell tube. As I mentioned before that's what it's for, It holds the cable outer in place. As for the carb end, it shouldn't take much imagination to make a suitable end that fits in the bracket. Take the car to a decent bike shop and show them what you have and what you need. Easy Peasy
Cheers John
JOHN HALL & JULIE ROBERTS

Ok, I'm back. The honey-do list had some mission creep (don't they all)...

Les: I've added the top shot you wanted to see. The throttle cable is removed so I could get a true measure of its length. The cable fitting is in line with the throttle and FWIW, both butterfly valves open when they're supposed to with the current set-up. The bracket fitting points to the cable attachment point (centered over the rear intake pipe) and you can see the choke cable coming in from the right.

Charley: The plastic/metal fitting on the carb bracket has a constant interior diameter. The tube diameter is too small to fit a cable sheath inside it at either end. The outer diameter is larger where the threading was added for the nylon ring. The nylon piece is simply a threaded washer/bushing that functions as a retainer. I don't know the origin or original pupose of this piece if it was meant for something else.

Prop, Chris, and John: I went to a bike shop and picked up some cable. I expected to get some quizzical looks from a kid, but it turns out the owner had a Sprite and a Midget several years ago and knew exactly what I was talking about. After the usual banter about oil leaks, marking its territory, and Lucas: the Prince of Darkness, he said I should use a piece of gear change cable. It's thinner and the good ones have a teflon interior that reduces friction. They also have a heavier spiral wire wrapping. This makes them stiffer and more robust, but harder to cut. He gave me a 20" long piece of scrap cable at no charge. I will work on it this afternoon.

Thanks for the input everyone. Any other suggestions gratefully accepted.

Cheers,

Glen


G. D. Phillips

it must have been hell to control that engine with the cable stretched between the footwell floor and the carb

every time the engine rocked the throttle setting would have altered, cos the whole point of having a cable inner and outer is to allow flexibility and movement without affecting the settings involved

somebody was having a "bad brayne" day when they installed it that way

You may find that a gearchange cable is a little over engineered for that task but having a slimmer outer it will allow an easier job when cleaning out the recesses

I suggest lubing the cable with graphite powder to keep it running slinkysmooth

Good luck

(funny how where ever you go someone once owned a Spridget, or their cousin, best friend or their dad.)
Bill sdgpm

Glen,

If the end of the metal threaded fitting in the nylon bush is the same inside diameter all of the way through (same on both ends), is its outside diameter large enough that you can drill it out (about 1/4 inch deep) to accept your new cable sheath?

Charley
C R Huff

Charley,

It may be big enough to drill out; not sure if I can drill out enough. Now have new cable, sheath, and some misc fittings. Have to check later; today is anniversary, so nothing is happening Midget-wise.

Glen
G. D. Phillips

GD I had a sticking throttle on mt HIF carbed IOW Frog. I replaced cable, carb return springs, used a gallon of WD40-- still no success. The solution was a seized up throttle pedal (Organ Type) Removed. freed up well lubricated - Job done. I know it seems crazy, but it, sadly was the LAST thing I tried. All The Best
Roy
R Cole

Ok, I'm back. Haven't had a chance to work on car owing to anniversary weekend. Near 100 temps aren't helping either.

So... Roy, I started checking things at the pedal and worked my way through the linkage, cable, and carb. Pedal hinge and linkages seem ok, but I'm not sure how loose it's supposed to be in the first place. Carb side is ok too; both butterflies open when they're supposed to - first the small primary, then the larger secondary. The throttle closes completely when tension is taken off the carb bellcrank.

My plan is get on the car after some yardwork tomorrow.

Cheers all,

Glen
G. D. Phillips

OK, so here it is 100 degrees in my part o'Texas and the air conditioning has crapped out. As of 2000, it is 100 outside and it has slowly warmed up to a balmy 91 inside. The ceiling fans are working overtime...

In the meantime, I have drilled out the fitting on the carb bracket to accept one end of the cable sheath. I have peeled away a length of cable sheath to fit inside the tube coming up from the footwell roof. I have also added a short piece of hard tubing over the footwell tube to support to further support the sheath.

At that point, my called me for dinner.

I do not miss dinner...

More tomorrow (and some pics).

Cheers,

Glen
G. D. Phillips

Ok, the house A/C is fixed and, wouldn't you know it, the outside temp has plunged to the mid-90s...

I seem to have fixed the problem. A local bike shop gave me a scrap piece of gear change cable saying that it had a smoother teflon interior. I trimmed the cable to the proper length and shaved off some of the black plastic outer sheath at the tips. I then drilled out the fitting on carb bracket and used a thin round file to ream out the cable tube on top of the footwell (the drill wouldn't fit). This is allowed the cable to socket into the fitting and tube. The cable is slightly long and under some tension, so its own pressure keeps it in the sockets. I also added a piece of plastic tubing over the footwell exit point to keep the cable straight before arcing over in a gentle curve to the carb fitting. The final hookup was easy - both carb throats open up when they're supposed to. A test drive was great - no more racing engine - and the pedal has a totally different feel to it.

Thanks to everyone for their ideas and suggestions.

Pic below

Cheers,

Glen


G. D. Phillips

Easy Peasy!!
BTW, the bolts in your pedal box cover should be 1/4" unf set screws if you want originality.
Sorry for being pedantic.
Cheers John
JOHN HALL & JULIE ROBERTS

Aah, John, I know the screws aren't correct. PO had three (count 'em) different sizes of slotted and cross-slot screws in there, one of which was too small and just sort of rattled around in the hole. I used what I had in my parts bins. My one concession to formality was squaring the slots.

Cheers,

Glen
G. D. Phillips

This thread was discussed between 17/06/2009 and 02/07/2009

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.