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MG Midget and Sprite Technical - Cotter pins and wishbone mounts

Hi all.

I am (at last) busy dismantling the front suspension on my midget, but have a couple of problems, for which I would be grateful of some advice.

1. The cotter pins which prevent the fulcrum pin from rotating itself, where the kingpin is attached to the wishbone pan. Can't budge either of them. The manual says "tap them out", but they aren't moving. Are they rusted in from above, or am I missing a trick?

2. One of the wishbone mount bolts was totally seized in the bush insert, so I had to brutalise it to get it off the car. Since doing so, I notice there is a small crack in one of the mount points on the car. I can't see a repair panel for this, is it just a cut out and weld in a new one of my own making job?

Thanks in advance,

Hi David

Most people have problems with these blighters.
Best approach is get the pan on a good steady surface. Back face of a large vice or solid concrete floor. You need to leave room underneath for the cotter to come out of course. Then with a decent sized pin punch, something like 1/4", or something metal around the same diameter, give a sharp smack with a fairly good sized hammer. Its all about getting the maximum punch in a nice straight line. The cotter pin is tapered so once you break the taper it should fall out. If this doesn't budge it get the blow torch on it for a of minute or so, this may also help break the taper.

As for the cracks, if the metal is just cracked and not thinned due to corrosion you can drill a small hole at the end of the crack, this stops if from getting any bigger, clean the metal up and weld the crack.

Hope this helps


S Ricketts

What Simon says is right in that there is a taper but the pin itself is a round stock bar with the taper ground on it

It can only come out "upwards" from below as the taper is inserted from above to lock down with the ridiculous little nut

If large smacks with a BFH dont shift it you may be better off to remove (ho ho - not) the wishbone and hub unit in one go and address the removal on the bench/floor

Bill 1

Thanks for the guidance.

The wishbone/kingpin assemblies are already on the bench and just these damn cotter pins to get out, so I can finish dismantling the lower fulcrums.

Is the alignment of the lower fulcrum bolt critical? As obviously there is some rotation in it before the cotter pin would prevent further movement? Presumably I should be able to rotate it a few degrees using a big screwdriver on the end?


The cotter pin should be wedged firmly against the flat on the fulcrum pin, preventing it from turning, although the two (and the kingpin)will move together relative to the wishbone.

A quick way is to use a thin slitting disk in an angle grinder to cut through the fulcrum pin either side of the kingpin - in the gap that the cork washers go in. The parts will then come apart and enable you to drift the bits out separately which is much easier.

Guy Oneandahalf Sprites

<<The parts will then come apart and enable you to drift the bits out separately which is much easier.>>

Drift out which bits?
Dave O'Neill 2

"Drift out which bits?"

I think what he meant to say was, "screw out the bits", as the lower fulcrum pin is threaded in the wishbone pan.

Once you get it apart, if the threaded pin parts are not a very snug fit into the wishbone, plan on replacing the wishbone pan, as the threaded parts of the pan are softer than the hardened pin.

Norm Kerr

Sorry, trying to be brief! (which is unlike me!)
If the fulcrum pin is sliced through the kingpin is then detached from the wishbone. It is easier then to hold in a vice to work on. The center piece of the F-pin can then be drifted out of the kingpin. This is generally easier than drifting a solidly stuck cotter pin as the bit of fulcrum pin is large enough to give a good whack with a drift and FBH. The small cotter pin distorts too easily when hit hard.
And yes of course, the two ends of the fulcrum pin will just unscrew from the threaded wishbone bearings - if they don't just drop out!
Guy Oneandahalf Sprites

When you reassemble the front end, put a little anti-seize on the cotter pin. you may need to take it apart sometime in the future.
J Bubela

Thanks for all the help.

I went and bought a blowlamp and some sturdy F-clamps so I could stop them flying around the workbench. Heated them up for a bit, beat the sh*t out of them with a lump hammer using a bolt as a punch... nothing. They are pretty well stuck.

I guess I'll have to do it destructively now. Is there any mileage in trying to drill them out, rather than going in for the kill on the fulcrum pin itself?


Since you are likely to need to replace the fulcrum pin anyway, then to me that is expendable which is why I would cut it. I know that if I was doing it I would probably end up damaging the kingpin if I tried drilling out the little cotter pin!

The other option - if the fulcrum pin bushes are worn anyway, is to get a complete wishbone and kingpin assembly on an exchange basis. In which case you just send the whole thing off as it is and let them dismantle it!

Guy Oneandahalf Sprites

I'm with Guy on this one.

There just isn't much point it trying to get it apart because once they get that bad they really aren't that much good anymore and need replacing. Since pre-built assemblies are very competitively priced, it is so much less hassle to have someone else do it all.

Norm Kerr

I'm a bit curious about this, have you been smacking the end that had the screw thread on it or the blank end?

This makes a difference as the blank end is the "can't drop further in" end of the pin that holds on the taper and it can only come out one way, t'other way just hammers it in harder

You need to hammer seven bells out of the end the thread was on that probably broke off three weeks ago when you tried to undo the rusted on nut

Just a thought 'cos you have prolly done both ends to death by now

What Guy (and Norm) suggests is actually the best bet for you as the wishbones will likely need more love and attention too and may have been holding the car off the deck for "Umpteenty" years

Some of the MG suppliers may have these assemblies ready to purchase on an exchange basis
Bill 1

I'm definitely trying to remove it in the correct direction, and the little nuts came off dead easy on account of being protected under a mountain of grease.

The whole assembly is moving pretty freely, so it's not all seized through a lack of lubrication.

I am wondering if the orientation of the fulcrum pin is playing a part here? In the linked image, you can see that the pin is not centrally located in the hole, suggesting that the fulcrum pin has rotated and may be jamming the pin in the whole assembly? Of course, the fulcrum pin may itself also be seized I suppose...



The fulcrum pin has a small flat where it contacts the cotter pin - which also has a wedge-shaped flat. Unless the fulcrum pin flat is aligned with the cotter pin hole on assembly, then the cotter pin will not go in far enough for the thread to protrude and get the nut on. Your cotter pin is well through the hole so the fulcrum pin was aligned. It is normal for the cotter to be pushed to one side like that.

It all looks in quite good condition. I am surprised the cotter pin is still almost intact if you have been whacking it hard!

Is there a lot of slack in the threaded bearings between fulcrum pin and the wishbone? It doesn't look as if there has been excessive movement from the condition in the photo - I assume it does need to be dismantled?
Guy Oneandahalf Sprites

Is it the kingpin or the wishbone that you have clamped to the bench? The hammer blow needs to be directed onto the cotter pin and needs to be reacted by something heavy (the bench), otherwise much of the blow could be dissipated by 'spring' in the wishbone pan.

If the fulcrum pin is seized in the wishbone pan then you may need to replace that too. I have to say that I favour the 'complete wishbone and kingpin assembly exchange' option.

Jonathan Severn

Guy, you may be right, perhaps it didn't need dismantling anyway, I was just doing it as a matter of course, cleaning all the old grimy grease out of everywhere and fitting new seals.
It definitely needs it now I've burned the cork seals with the blowlamp!

I am striking down into the kingpin. Maybe I am being a wuss, but I was hitting it hard enough to deform the bolt I was using as a punch. In the attached image, the wishbone legs are wedged against the vice, and the clamp is preventing the kingpin from moving, so the fulcrum joint cannot articulate.

Hmmm, I wonder if I can get on it with a bearing puller, and try to push the cotter pin out...? After that, I'm getting the hacksaw out and start getting more sacrificial.



Keep persisting. You will get there and then will have devised the best technique for doing the other one! I wonder if you can get the corner of the jaws of the vice on it to press it out?

BTW, if you do end up cutting the fulcrum pin it will be slow going with a hacksaw. Do-able, but slow! You will need to unwind the fulcrum pin as far as it will go one way by rotating the kingpin. This will expose a gap on one side down past where the cork washers were. It is wide enough for access with a 2mm slitting disk in an angle grinder.

Good replacements for the cork washers can be made by cutting discs from dense foam pipe lagging. You can even fit them after assembly, using superglue to seal the slit edge. Sounds like a bodge but they are actually more effective at keeping out road grit because they can be cut oversize and compressed to give a close seal.
Guy Oneandahalf Sprites

1mm slitting discs are better for this job !
David Smith

LOL - checking the label, that is what mine are! I knew they were thin ones. Certainly better than a hacksaw anyway.
Guy Oneandahalf Sprites

If you hit the cotter pin with the kingpin set up like that you will lose most of the force you generate with bending of the kingpin

you need to support the shoulder of the wishbone /fulchrum/swivel pin joint across the jaws of the vice, (the plastic jaw faces will absorb some of the power you generate, I'd take them off if it were my vice) with the jaws open enough to let the kingpin dangle through

Then bash seven shades out of the cotter pin, hitting the threaded end to release the pin from the taper section

The action then takes place on the level surface of the vice jaws

You really should not be having this much trouble with the cotter pin

The real fun comes later with the fulchrum pins
Bill 1

Thanks Bill, I'll give that a go. I'd have thought I am getting enough energy into the pin, but anything is worth a try now!
I agree I can't see why they are putting up so much resistance, which is why I still have a nagging feeling I must be missing something...

Apart from a couple of seized bushes, everything else has come apart relatively easily. Not so sure it will be the case when I start on the rear suspension next!


"what will be the case when I start on the rear suspension next!"

don't worry, everything will come apart easily enough back there,

but most of the bolts will break off in the body and you'll have to drill them out (BTDT). Its what we call "therapy"


Norm Kerr

Good news! Bill wins the prize for how to get the cotter pins out. With them mounted directly in the vice, and good beating, they gave up.

Fortunately, the fulcrum pins came out nice and easily too. So now I've got them all apart and de-greased (brrr, that was chilly), and ready for painting prep.

Thanks everyone for your patience with me on this one! I'll be back with more on the rear end I'm sure - really looking forward to the rear wheel cylinders being a pain.



This thread was discussed between 17/11/2010 and 29/11/2010

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