Dragging clutch and hydrochloric acid

Three thingsthat have successfully cured a dragging clutch / difficulty in neutral selection with Commandos I've owned over the years :

Adjust clutch according to manual paying attention to correctly adjusted centre nut against pushrodand correct cable free-play at small actuating lever just inside gearbox cover.

Use 20 / 50 engine oil in primary chaincase.

If a thorough cleaning ofall clutch plates in petrol doesn't improve things , fit a set of new sintered bronze friction plates.

One or all of the above has always sortedmy dragging / neutral selection problems.

Cleaning them with acid sounds overkill and potentially disastrous. After you've cleaned them with petrol you could give them a quick scrub with washing up liquid and a good rinse. They will be very clean then.

As James says, just check it's set up correctly and it shouldn't drag.

Ian

Gentlemen,

Hydrochloric (HCl) is very, very nasty, have a look here:

https://melscience.com/en/articles/how-hydrochloric-acid-reacts-aluminum-formulas-and/

I worked in the semiconductor industry for far too many years and an HCl leak was always a disaster. Even SS-316 pipes and fittings grew green mushrooms with ppm leaks.

Also, the process of 'cleaning' aluminium with HCl creates a lot of Hydrogen, that is really dangerous. If in doubt ask NASA!

As Ian said earlier a bit of appropriate solvent & elbow grease or Vapourblast is the go!

Take care of yourself.

Rgds Steve

Previously steve_elston wrote:

Hi all

Stripped and cleaned clutch plates in petrol on my mk 3 last weekend

still having the usual problem of finding neutral when needed, normal carry on toe it up then heel it down ,just as it drops in the bloody lights change .

This is bearable if I'm on a long run as its not so apparent, but as I live in the croydon area it can be a right pain

A pal of mine suggested cleaning the clutch plates with hydrochoric acid to remove any old burnt on oil residue,then neutralizings the acid with an alkaline (ie baking soda solution)

Now my question is which plates should I clean the plain steel or the sintered bronze or both, has anyone tried this, advice please

I will add that as soon as I turn off the engine I can snick it into neutral no problem,

steve

Hi Steve,

You may now have a warped plate or two and I would suggest fitting a clutch pushrod seal to prevent gearbox oil migrating through into the clutch centre.

Dave

I had a similar grotty gear selection problem with my 750 Commando and, after asking for advice for a cure, fitted a set of sintered bronze plates.

Which........actually made the problem worse. I then replaced the bronze plates with a new set of fibre and steel which also did not help.

Eventually, I twigged that the problem was wear in the gearbox mainshaft bearings. If you heave in and out on the clutch body and it moves and clicks this gives a big clue as to their condition.

So all the box bearings were renewed, the original set of clutch plates re-used and the problem sorted.

I forgot, it can also be caused by an overly tight primary chain or belt.

It's probably the ratchet spring. Even new ones often need re-aligning (bending) to work properly. Old Brits have a good description. Basically you need the spring to not touch the pawl when it's at rest but have the tiniest of clearance so the pawl can move freely but the spring will engage as soon as you move the gear lever.

https://www.oldbritts.com/gearbox_a.html

The clip you are trying to remove is just like a bit of bent wire. Not really a circlip.

Ian

thanks Ian ,

guess I will have to keep trying !

which box are you working on?

Paul

Whereabouts in the world are you Roy? There may be someone nearby who could provide some practical help.

Ian

I am working on a 1972 commando 750 gearbox .

I am in the Hull area , Thorngumbald ( somebody has to ) .

First time I have completely rebuilt a gearbox and have learnt a lot . Any help or advice are always appreciated !

Thanks for all who have helped so far .

That ratchet spring is the cause of a lot of issues for such an innocuous looking part.

Excellent article, Ian. Having rebuilt a laydown box I can confirm that a lot of it is still applicable and useful.

thanks again Ian , the Old Brits article is very good and useful for reference re torque settings etc