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MG Midget and Sprite Technical - Throttle pedal

My 72 midget has just passed it's first MOT in 6 years after a fair bit of work and money. It was fantastic to drive a midget again after so long. There are however, a few teething problems I still have to sort out.
One of them seems so simple but I have tried every thing I can think of and still can sort it. I can't get the throttle pedal to move smoothly. I have removed the pedal and the linkage and cleaned and greased both. Without the cable connected they move smoothly. I have fitted a new throttle cable (after removing the inner cable and making sure it was well lubricated first) and this too moves smoothly when out of the car. The linkage at the throttle moves smoothly too even with all three return springs fitted but when all fitted together the throttle action is very sticky.
Does anyone have any tips to getting a smooth action?

Thanks in advance for your help.
D Brown

Cable routing - Can you post an under bonnet photo showing where the cable goes? On my '71 there's a heater pipe in the way as soon as it leaves the footwell.

Ant
Ant Allen

I have read that routing makes a big difference so I have removed the heater pipe. It didn'tamke any difference. I am thinking that I need a nylon lined outer cable.
D Brown

If you have the organ style pedal, you will find it beneficial to change it for a 1500 one. It is a straight swap. Also alleviates the problem of having the organ pedal go flat to the floor when the rubber nobule breaks on the back - unless of course you want to experience 8000+ revs and no way of hooking your foot under the pedal to release it. Not so bad when it happens when stationery - as it did with me - but whilst on the move is clearly not recommended...
Geoff Mears

One thing that I have seen on new throttle cables, is a burr on the inside of the ferrule at the end of the cable housing which can cause binding when installed.

Pull the inner out, and take a drill bit and use it to chamfer the edge of that hole. It ought not to take very much, just enough to avoid binding any more (you don't even need to get the drill out, just twist the bit with your fingers should be enough).


(personally, I am a fan of the organ pedal because it makes heel-toe downshifting a breeze).

Norm
Norm Kerr

What a timely post. I had a "sticky" throttle cable, too, and just a few days ago got a nice tip on the subject from another forum. I think it worked for me, so will pass it on. However, this is for a LHD car, so may be completely irrelevant for you. Not only has my cable not worked smoothly, but because of the way it is routed from footwell to carbs, it rubs on the underside of the bonnet. Because of the angle of the carb assembly, it has to make a fairly acute bend into the socket that holds the end of the outer cable. I was contemplating making some sort of bellcrank so I could pull from the side, but got this tip instead.

There is a metal cable guide tube used on bicycles that is bent about 90 degrees (the fellow at the bike shop called it a "noodle"!)with an inner sheath. It has a fitting on the end that fits perfectly into the area on the heatshield where the normal cable ends. I got one of those plus a piece of Teflon-lined cable cut to fit (Teflon-lined cable by itself may help). Cleaned and lightly greased the cable and put it all together. I think it works more smoothly now and I also think it does not rub on the underside of the bonnet. I couldn't get a picture of mine until I get home tonight, so I've attached a photo from the person I got the tip from. The end result is pretty much the same.

BTW, what is an organ style pedal? Is that what is on pre-1500s? If something breaks, wouldn't the throttle return spring prevent any 8000 RPM incidents? Unless, of course, your floor mat gets jammed under the pedal!

Jack


Jack Orkin

Great tip Jack. May not work for me as mine is RHD. I think I need a teflon lined outer cable. I hope that will improve things.
Now to get the engine running properly.

Dave
D Brown

You may have already covered these pionts - on my previous Spridget carb problems turned out to be a very slightly (hard to see) bent pedal hinge pin

I know you took the pedal out but did you remove and check the pedal hinge pin

and with present Midget, the hinge wasn't bolted to the floor properly

lubricating hinges and joints and cables are a part of servicing that often get forgotten too

Just my experiences
Nigel Atkins

Jack -

The "Organ Pedal" hinges from the floor instead of hanging from above. But the linkage it actuates is pretty similar to the pendant pedal.

Note to D. Brown - Have you checked the motion of the throttle mechanism at your carbs? Seems like you've examined everything else, but there's the remote chance you might have a perfectly good cable and pedal setup connected to a faulty linkage.

-:G:-
Gryf Ketcherside

Jack,
The organ type of pedal has a "?" shaped piece of metal that just pushes into a rubber section on the back of the pedal. The other end attaches to the linkage. But if the rubber splits where it joins the pedal, the linkage turns itself inside out and literally jams the pedal flat on the floor, which in turns opens the throttle wide. As it is jammed, return springs cannot over ride what has happened.
Geoff Mears

Nigel, I took the pedal off and it was very stiff. The bracket that bolts to the floor was bent and the hinge was stiff. I cleaned, straightened and lubricated it. I thought that was my problem! The pedal linkage was also very stiff. Once cleaned and greased it was/is a lot better.
Geoff, I don't like the idea of having my throttle jammed open. I am now thinking of the 1500 pedal. It won't fix the current problem but is worth thinking about.
Gryf, I am pretty sure the carb mechanism is ok.
Off of the car everything is ok. I am coming round to thinking that when the pedal is pressed there is too much friction between the inner and outer cables (despite it being new and well lubricated). I checked this off of the car but it could all change when connected up to the carbs and the three return springs.
D Brown

Did you take the pin out and check it with a magnifying glass or roll it along a flat surface the bend in the pin can be very small - sorry to be picky

I'd bought new linkages for mine before a real expert found the simple fault of the slightly bent pin and it took him tree quaters of an hour to track it down, he remembered having the same fault on a Leyland van

Perhap a photo of the cable fully in situ in the engine bay and if at all possible a photo of it connected to the pedal from behind and pedal arms and links

Perhaps someone will spot something
Nigel Atkins

When I rebuilt my Midget, I replaced the throttle cable with a new one, but it was then too stiff. When I checked the length against the old one, I found that the outer was about an inch shorter, so I brought a third one, this also was shorter than the original.
I got round the problem by using the old outer cable, and a new inner one, and its been like that ever since.
I think there is a batch of short outer cables out there.

I tried the 1500 pedal, but couldn't get on with it, it was stiffer than the organ pedal, so I reverted.

Dave
Dave Barrow

We have been running the same setup as Jack for 2 years now on Will's midget without any faults whatsoever.

So yes it does definitely work well for rhd cars too - well those running an 1"3/4 SU anyway.
PeterJMoore

sounds like the trottle bearing are worn out.. LOL HAHAHA... sorry!

Seriously,

look to make sure the cable isnt riding agianst the fuel hose that connects the 2 carbs toghather


also make sure that the 4 springs have not gone flat,,, that can make a differance as well.

choke return spring, carb springs (2) and the throttle spring
Prop

I purchased another new cable last night, this time from the Mini Spares Centre. It is longer and has a nylon sleeve in the outer casing. The routing is better now, it goes over the top of the air trunking, and the throttle action is now nice and smooth.
Sorted.
Now for the misfire.


D Brown

This thread was discussed between 28/06/2010 and 29/06/2010

MG Midget and Sprite Technical index

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