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MG Midget and Sprite Technical - Accelerator / Pedal stiff and notchy - Suggestions

MK1 midget / 1275 engine.

Always been a bit stiff and notchy, would like to lighten it up a bit and get some smoothness into it. 3 springs on the carb linkages as specified, but happy to get new ones...When disconnected the angled lever from pedal to cable is nice and floppy.

Thanks

Tim
Tim Carter

Sounds like you are proceeding on the right lines by disconnecting the parts and testing each separately.

- Pedal pivot in the floor can rust and get stiff.
- Cable outer can also rust, kink or otherwise make inner stiff to move.
- Butterfly pivots and linkages on carbs can wear, if car not driven for a long time perhaps also gum up.



AdrianR

Sounds like you need a new cable--if the springs are the std springs.
William Revit

Pedal hinge also floppy and free moving.

Cable as new. Should I grease it internally?

Car not used much, regarding gumming up, they (the carbs) are coming off soon, so will check this, along with linkages, and will get new springs.

Maybe just too used to my 'fly by wire' pedal movement on the Volvo ? ;)
Tim Carter

Tim,
long shot but is the pedal hinge assembly worn? It may well be floppy when disconnected but then be 'awkward' when under tension after connecting to the cable and springs?
Ignore obviously if it's a new assembly.
Jeremy MkIII

Tim there is another possibility which I had on my 1500 years ago. With tickover set quite low the butterfly discs were closing fully and effectively sealing against the carb throat. As the running engine was still drawing air this was creating a vacuum - or at least a negative pressure wrt ambient, needing a bit more pressure on the throttle pedal to overcome the vacuum and open the butterfly. In practice this caused a jerky start as it was difficult to control especially in slow moving traffic. At first I got into the habit of thumping my right knee with my fist to get a smooth start! The solution was in fact simply turn the tickover up a fraction so that the throttle discs never fully closed and sealed.
GuyW

I found the cable on my 1500 was very notchy so I replaced it with a new one which wasn't much better. I then replaced it with a bicycle brake cable, these can be bought in long lengths and cut to suit. The advantage of this is they're Teflon lined and the cable is Teflon coated. This made for a very smooth cable and it's the only thing I would fit now.
R.A Davis

Many thanks, some useful comments and suggestions.

If it ever warms up, I will get to work!
Tim Carter

When replacing the cable, pull it out of the sheath and coat it with engine oil. The original cable on my 1971 lasted about 10,000 miles before getting sticky. Oiling the replacement had it last for about 100,000 miles.
Glenn Mallory

I'm with RA Davis on this. The original type cable is a PITA. I had trouble with mine for a long time (1500 car, but no different for A series).
A new OEM cable from MGOC spares was nearly as poor.
The solution was a cable I made up from a Venhill universal kit, which is a teflon cable like a pushbike brake cable but a wee bit sturdier.
Absolute game-changer. Brilliant kit and cheaper than OEM.
(Or they were then. I see they have gone up a bit since).
I've since made up throttle cables for other people's cars from the same kit and all have been perfect. It's about an hour's work and super-easy.
The adjuster in the Venhill kits I used, basically the cheapest option, is metric threaded but you don't have to use it. It will happily accept the original Imperial adjuster.
But checking just now I see there are Imperial versions.
I too would not use anything else now.

http:www.venhill.co.uk

By the bye many A series owners retrofit the pedal from the 1500 which is apparently a better design, but I have no experience of this personally.
Greybeard

@Greybeard, bought one, in fetching orange!
Tim Carter

Good show Tim, and best of British with it.
I did notice that they are now available in different colours. When I used them you could have black or black, take your pick!
For what it's worth I suggest you have a good look at the hole in the firewall where the cable goes through. The metal is a bit thin and it can easily get pulled out of shape so that the cable ends up running at an angle instead of straight. I had this issue with the 1500.
My solution was to pass a two inch screw through with a nut either side and tweak the panel straight again. Made a lot of difference.
It's easy to see if the panel is distorted because there should be a pressed "dimple" with the cable hole in the middle.
If it's not straight it can cause the cable to drag enough to overcome the springs and prevent the throttle closing cleanly.

See also Guy's post about the butterflies. It's an excellent point and I've fallen foul of this before now, - he's spot on.

(He usually is...)
Greybeard

Also had the same issues and after reading several discussions on the problem I bought a new Venhill cable a good four or five years ago, it fixed the problem and gave nice smooth acceleration ever since.
Tim Lynam

Thought I would ask, is there a preferred / desired length for the outer cable? The one on the car is 28" (71cm), seeing anything from 24" to 35" for cables on the net. Don't want to cut my new cable too short...
Tim Carter

Tim, there is plenty of length available in the kit. When I did them I laid out the outer for the easiest route with minimal bending and went with that. It turned out a bit longer than the factory fit cable but not a lot.
It will be different for you; I did it for a 1500 but your A series car wears it's carbs on the wrong side 😉
In short I don't think it's critical; whatever you think fits best and doesn't interfere with anything else will be fine. There's plenty to play with and it's nicely flexible.
Greybeard

I took my old cable to a bike shop and they made up a teflon lined one, exactly the same length as the original, and even put the ferrule on the end and soldered over the carb end. Cost me £10 and huge difference!
aj robinson

Venhill will also make a copy of your cable if you post it to them, with any changes you request - they will also retain any original parts that you ask them to and swap them over if they are serviceable.
S Macfarlane

This thread was discussed between 13/02/2025 and 17/03/2025

MG Midget and Sprite Technical index

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