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MG Midget and Sprite Technical - Sticking choke - frogeye

Hi
I guess I know the answer to the first part of this question, but thought worth asking.
I am finding the choke levers on my frogeye (standard SU's) dont quite fully release, particularly on the rear carb. When releasing it, I can always subsequently push the lever up a little bit further with my hand. I assume thats not right? The springs on the sides look ok.

I refurbished the carbs only three years ago and I'm guessing I just need to do it again or is there something else I should check first?
I assume its the modern petrol that causes the problem? Is anyone else finding the same?

I think I will try and do it with the carbs in situ, which I am guessing is possible, as they are quite accessible.
Only thing that worries me about the job is getting the jet centred afterwards. I find it very hit and miss.

Thanks, Graham
Graham V

I had the same issue with the H4 carb on my frog. It's as if the free length of the spring is too long to pull the jet fully home, so I "squashed" the hooks at the top and bottom of the spring to make the spring a bit shorter. It's better but not perfect. Thought about bending the choke lever at the spring end but worried that it might snap.
Simon Wood

You could try fitting a Morris Minor choke cable centre. The Minor had a solid centre so if you fit it so there is some surplus length you can push it in and push the choke levers back. The Frog used a braided choke cable so it is impossible to do this and it had to rely on the spring tension.

Rob
MG Moneypit

My frog has always had a solid cable. I think the braided version is aftermarket.
Bob Beaumont

My 59 Frog also has a solid cable so, as Bob says, probably aftermarket or a DIY fix by a PO.
Martin

Thanks for the feedback and apologies for delay in responding. That's very interesting. Yes mine has a solid cable too, and like an idiot had wondered what the purpose of the pin and collar above the stirrup was for. So like the idiot I am, I didn't bother refitting it, as I couldn't see any purpose served!
So thanks for the advice. I will put it back and see how that helps, although there is quite a bit of friction when returning it by hand.

Thanks, Graham
Graham V

I found liberal lubrication of the cable helps!!
Bob Beaumont

I think maybe I spoke too soon. Having looked at the parts diagram (attached) there appears to be nothing to push down the stirrup (27) when releasing the choke, even though the cable is solid. So not really sure of the purpose of a solid cable, as it appears it should just slip through the stirrup.
(The part I removed thinking it was redundant, isn't shown on the parts list)

Bob - Thanks for the comment but pretty sure its not the cable thats sticking as there seems to be friction in the choke mechanism itself.



Graham V

I had friction in the cork rings after 16 years. Viton rings leaked, the new burlen rubber rings were sticking, so I returned to cork.

Flip


Flip Brühl

Cork it is then. Thanks
Is there any need to remove the carbs? There is plenty of room under a frogeye bonnet so I thought I would replace the jet bearing seals whilst in situ. Will that work do u think?
Graham V

And one other, perhaps obvious, question please.
Should the collar & pin above the stirrup ( connected to the air filter bracket) lock on to the outer cable, or should the outer cable sit above it and simply allow the inner cable to slide inside the collar.

Or maybe the outer cable should have a tapered end that sits inside the collar and mine is missing?

Thanks, Graham
Graham V

The only reason to let the carbs on the manifold is that the synchronization of the carbs stays intact. Personaly I would remove them to work more accurate.
For your second question see photo


Flip Brühl

Thanks for the photo Flip. I couldn't quite make out the details but have since also looked at the picture on the Moss site, and so think the outer cable has a tapered end to fit inside the collar. If so, I guess I need to buy a new cable to go with the new cork washers!

I still don't understand the importance of the solid cable (as opposed to braided) as the stirrup prevents a direct connection between the cable and the choke levers, and so pushing the choke knob in doesn't force the arms down, but they must rely instead on the springs to go down. Is that right?
Graham V

the solid cable pushes the arms down as does the springs.
Flip
Flip Brühl

Flip
Sorry if I am being stupid, but I don't understand how it pushes the arms down when releasing the choke. It is not directly connected to the arms, or at least I don't think it is.
I thought on engaging the choke, the cable will pull up the stirrup, which is connected to the arms, and so pull up the arms.
But on disengaging, the cable will simply release the tension on the stirrup, as it slips through the hole on the top of the stirrup. So all the work to release the choke is done by the springs

Or have I misunderstood it?

Thanks, Graham
Graham V

Graham,
Yes I think that you are correct. When my frog had H1's the choke stirrup arrangement was as you described: The cable only pulls the choke levers upwards. It is the springs that return the choke levers as the cable is not physically connected to the stirrup.
Simon Wood

Thanks for the confirmation Simon

And now just reporting back generally. Have made a very simple, but temporary, fix and now the choke lever returns all the way, every time. Works great!
See the attached picture, although the purists better look away!

Also discovered the collar and pin that fastens on the choke lever cable at the carbs (at least on my set up as it may not be original), was installed the wrong way up by the PO. Much easier to use the choke lever now.

Thanks for all the various input. So helpful having a community to talk things through with.

Graham



Graham V

yes Simon and Graham you are right, it is the spring only
Flip
Flip Brühl

This thread was discussed between 24/05/2018 and 31/05/2018

MG Midget and Sprite Technical index

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