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MG Midget and Sprite Technical - 1500 throttle jerky

Hi Guys, Every car I have ever driven with the 1500 triumph lump in always seems to have a fairly on / off throttle I think it must be that strange linkage ?

Anyone ever cured this ? I took out the cable last night and ran some oil through it plus lubricated the pedal, linkage everything I could see and its still bad.

Maybe fit a plastic lined brake cable from a mountain bike ?

What about bining that funny linkage and wiring it up directly like a 1275 which seem fine ?

Ben Brown

ben

i can help you had the same took me weeks to get it right
e mail me for my phone nr
you have to do a bit of diy on the cable
mine is now spot on like it should be
the cars been out three times this week and goes well
bj camp

you didn't fit a toyota throttle did you???


LOL
Mick - trying to sort the wiring

Hi Ben,
I had exactly the same problem. I tried a few different things, including new standard cable, all without any improvement. Then I fitted a good quality mountain bike brake cable and I've never had any more problems. Its a lot easier than trying to modify pedal linkages and costs next to nothing.

Ben.
B Whiteley

Same problem, same solution as Ben - nice teflon cored outer with a stainless inner. Think I actually got it out of halfords in the end, cheaper than my local bike shop for some reason. I did get a couple of nice 90deg bend 'noodles' with adjusters on them, made setting it up totally painless:

http://www.sjscycles.co.uk/product.asp?pf_id=18060

I put one on the original brass olive thing that pokes through the top of the footwell and think I put one where it enters the actual mechanism at the carbs(can't remember). That bunch also do the npples for the end:

http://www.sjscycles.co.uk/product.asp?pf_id=8145

of which I used 2, to make sure nothing untoward happened. Another alternative I've seen is to get the metal bit out of electrical connector stips (chocolate block) and use that as it has 2 screw already.

Been fine ever since! One word of caution, make sure you use mountin bike brake cables & not gear cables - much thicker & more resilient.

-Craig
C Robertson

Have you hung it on the washing line so the oil can drip down gently overnight? That seemed to work perfectly for mine.

See - it's not just the kitchen that gets used for car parts!
rachmacb

Rach, your house must be a funny place to see! :)
All that horse and midget stuff al over the place...
How did your mom respond last weekend?
Or did she clean up the place for you? LOL!!
Arie de Best

LOL - I turned my back for a moment, and the kitchen was totally changed around! I am still finding things in the wrong places ....

I sorely missed your lesson on origami and pretty folded napkins - I think you should make sure you bring some to Silverstone so that I can put them in the picnic basket on the back of Primrose!!!
rachmacb

In the picnicbasket?
On the back of primerose!?

Oh no, there i was thinking you are a "cool" chick... LOL!!



And btw, you dont need napkins in a picnicbasket, just a bottle of Domperignon and olives. ;)
Arie de Best

LOL - it's like taking sweeties from a kid ;)!

There - you see - picnic baskets CAN be cool :) although, in this weather, even Dom Perignon would be nicely cooled on the back!
rachmacb

oy, stop taking my sweeties!!


No no no, if you wanna be cool have the Dom Perignon in a standard on the rearshelf behind the seats and the blanket in the boot.
No basket!!!
Never seen 007 carry a picnic basket on his Aston-Midget did you? ;)
Arie de Best

LOL perhaps, but I have fond memories of my parents picnic basket - and it WILL be mine one day :)

No, but then, I don't think I ever forgave 007 for riding down the slopes on a cello case ........, and there really wasn't any room in that for even a tiny bottle of Dom Perignon!

If you shared, you wouldn't need them nicked!
rachmacb

If you wouldnt have nicked them i might have shared them. ;)


In defence of 007: he didnt have the bottle of DP in the cellocase because he drank it to help him getting brave enough to decide doing the Super-G in the cellocase.
In my experience sliding down a hill on a cello is faster then using the cellocase.
I like to try a piano one day if it wasnt so much work to get it up the hill at first. LOL!!!
Arie de Best

LMAO - oh I would SO like to know how you know ...... and, I always thought that there were too few curves for SuperG - perhaps the Russians should have shot better, then it would have been upgraded!

I think that he let the side down, everyone knows that you only get brave from a warm pint of beer - before you go and face the blacksmith from the next village hurtling a cricket ball in the general direction of your face!
rachmacb

Just thinking on this one again - a good way to isolate the fault to the cable in a case like this is to disconnect the cable from the throttle linkage, and then rotate said linkage through its full range and feel for any sticking, binding, whatever. If movement is smooth and unhindered, then you know it's the cable and can act accordingly. The same would go for the pedal assembly.

Cheers,

-:G:-
Gryf Ketcherside

Yes it is definately a cable problem as twisting at the manifold is smooth.

I have ordered a low friction plastic lined mountain bike brake cable from eBay

Good call about using a chocolate block inner as a clamp hadn't thought of that.

What about at the pedal end as my brake cable has a barrel on it not a cone ? I guess the easiest will be to file it down to a cone shape.
Ben Brown

Ben,
When I had my 1500 I had "Sticky Throttle Syndrome" that turned out not to be cable related.
The problem in my case was that the butterfly disc was sealing too well when shut. On tickover the induction manifold depression downstream (engine side) of the butterfly was developing a suction on the butterfly momentarily preventing it from opening. It made starting off and particularly driving slowly in traffic quite difficult and I developed a technique of banging my right knee with my fist to move the apparently sticking throttle.

The solution though was to just turn the tickover screws up a tad, just sufficient to lift the butterfly off the dead shut position. Simple, tch!

Guy
Guy Weller

Ben,
Quite often brake cables come with a 'pear' on one end and 'barrel' on t'other, you simply chop off the one you don't need. You can pick up an inner with the correct fitting for a couple of quid, that's the route i'd go down. Or, you could get a suitable sized tube & slide it right down the inner where the barrel will holdit in position. If you were going for that, why don't you cut the end off the original cable & drill out a 1-2mm hole & use that?
-Craig
C Robertson

Ben -

As for the sticky throttle plate, I ran into something like that myself. And the problem wasn't with vacuum at all, as the carb was on the workbench at the time. Turned out that when I'd reassembled thing with a new throttle shaft, I'd tightened up the throttle plate screws before I'd allowed it to actually swing shut. It was misaligned just enough to bind when closed. So I loosened the screws slightly, closed the throttle, and then re-tightened the screws. That fine-tuned the plate's position on the shaft relative to the carb throat, and allowed it to close completely without binding.

-:G:-
Gryf Ketcherside

Hey Ben, did you get the sticky throttle sorted?

-:G:-
Gryf Ketcherside

Well I finally got round to fixing my throttle, have been side tracked by the numerous other jobs that need doing on the Midge.

Firstly great bunch of ideas on this thread really useful.

Anyway here is what I did. Bought a low friction lined rear mountain bike brake cable off eBay for £5. Cut a 5mm section off a 4" round wire nail and drilled a 2mm hole down the center of it. Threaded this small tube onto the start of the cable to convert the large barrel nipple to fit the accelerator pedal. Then threaded the inner through the bulkhead from inside the footwell as the barrel is too big to go the other way. Then cut a nipple off the old cable and pulled off the two brass ferrules at either end these needed to be drilled out a tiny bit too take my slightly fatter MTB cable, fitted these to my new cable at either end plus the two nuts and U bracket at the carb end. I then cut the plastic off a small 5 Amp electrical cable terminal block (choc block) and used this as a nipple at the carb end with its twin screw clamp.

Fired her up and runs a treat smooth as you like well pleased. The MTB cable was usefully longer than the standard cable and enabled a me to run it forward past the carbs and around in a nice wide arc under the thermostat housing and back round and over the rocker box. Clipped it to one of the coolant pipes to keep away from the fan.

In all took about 20 minutes, well worth it, and thanks again for all the ideas the nail and choc block were particully good :-)

Ben Brown

i had the same problem on mine .how iv resolved it was to bin the cable and sheath and buy a good quality bike brake cable.then rather than put it back in the plastic sheath i routed it inside a length of copper fuel/brake pipe so it is quite loose inside.iv done about a 1000 miles since then and its a diffrent car to drive, smooth as any modern car throttle. it worked for me and only took about 40mins, try it.
roy judd

it dont look to nice but if it stays as smooth as it is at the moment il redo it and make it look better.


roy judd

HI Roy, I think you might get metal fatigue in your copper pipe over time and it split somewhere near the middle due to engine movement on its mounts under acceleration / deceleration. If that happends I would recomend going the MTB bike brake cable route.
Ben Brown

ben its lasted over a thousand miles so far.to be honest the car is just a toy and is used when the suns out so i do a hundred miles or so a month.if i have to change the pipe twice a year its a small price to pay for having a nice smooth throttle.i did try a new throttle cable then a bike brake cable but it was still jerky.iv got a couple of other ideas i might try using a pully but im still having a think about it. ohh my brain aches from the strain lol.


roy judd

I came across this thread yesterday. I have had the same problem. I had gone out and bought a new throttle cable but still the same sticking problem.
Today I followed the advice in the thread ie halfords brake cable chocolate block connector ect Just been out for a run what a difference! Thank you all for making my MG drivable again.
D A Tower

It's not a linkage problem it's a cable alignment problem.

The Spitfire 1500 has exactly the same linkage (but a different cable) and doe NOT suffer a 'jerky' throttle like the Midget 1500.

The best solution is to make sure the cable bends are as wide a radius as possible and use a cable with a teflon lining.
Deborah Evans

can i say that my "bodge" with the copper break pipe is still working fine after nearly 3000 miles and is still as smooth as it was when i 1st did it.
roy j

This thread was discussed between 07/03/2010 and 02/06/2010

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