The stop on the end of the throw out bearing plunger is there to stop excessive force on the end of the crankshaft damaging the crank thrust bearings. It needs to be adjusted first before the clutch lever arm stop clearance is set to 0.020" for diaphragm clutches. (0.060" on cars with coil spring clutches, not diaphragm clutches, 850s etc)
To adjust the throw out stop, back off the stop, pull the clutch arm towards the inner guard as far as possible (a bit of a lever may be necessary) then screw the stop up hard against the clutch cover/WOK and then release the clutch arm. Screw the stop up by one more flat and then tighten up the lock nut.
If the engine is out of the car the easiest way to do this is to lie on the floor and put both feet up against the clutch cover and pull the clutch arm towards you.
Why do you need to do this?
The diaphragm clutch cover has 3 brass stop pins that prevent the clutch cover travelling any further towards the flywheel. If the throw out stop is correctly adjusted it stops the stop pins from actually touching the flywheel and forcing the flywheel and crank up against the crank thrust bearings. Any further travel is prevented because the throw out bearing stop hits the clutch cover first.
Once this has been done you can then adjust the clutch arm clearance to the required clearance.

If the clutch isn't releasing until the pedal is almost on the floor then there is wear somewhere, the clutch adjustment is wrong. (arm or throw out stop) or there is air in the system.

Places to look for wear

clevis pin in clutch pedal
clevis pin hole in clutch pedal
clevis pin hole in master cylinder push rod
clevis pin in clutch arm
clutch arm clevis pin hole
ball end of clutch arm
bent/broken ball end on clutch arm
hole in clutch throw out plunger
Some time it is also necessary to remove the spacer under the clutch master cylinder where it bolts to the cross menber although not all Minis have the spacer. This moves the master cylinder and push rod closer to the pedal and moves the piston up inside the master cylinder and reduces the free travel before the compensating port is closed off. However if it is too close it can cause the piston to cover the compensating port in the master cylinder and that is not a good idea.

Hope this helps
RonR

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68 build Mk1 Cooper S
72 Clubman GT project. Total restoration required

excellent write up miniron...

is it the overthrow stop nut and lock that some mini people say is now redundant ? i have seen a thread on another forum where someone said those two stop nuts were loose and one of the answers was take them off.... pretty sure it was pre verto?

My 2c worth..
1. If using a lightened flywheel, those 3 brass pins in the cover are nowhere near the flywheel face.
2. As the diaphragm spring goes beyond flat during disengagement (which is should if set up correctly, ie flat when assembled) the end thrust on the bearing REDUCES, not increases.
3. Most racers I know fling the 2 stop nuts. They may have a use with coil spring clutches, but who uses one these days?

[edit] BTW I've run mine for years with no stop nuts, no arm return spring, an orange dot diaphragm and later type 7W5-8 bearing.
The clutch now self-adjusts (same as a Verto one does) and nothing has worn out yet.
If or when the bearing carks it I have a flat Timken 3W5-8 one to go in.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Cool thanks for all the tips guys.

I have replaced the clevis pin at the pedal to M/C, Ive replaced the slave cyl pushroad, Ive replaced the clevis pin at the pushrod and clutch arm, Ive replaced the clevis pin at the clutch arm to clutch housing. I reckon that clutch arm is a million years old.. I did remove it just to inspect it and the ball was still on the end. I did notice some wear on it, but no idea if the angle etc is still correct. I think for the money, I might as well just replace the clutch arm also.

The throw out stop nuts are adjusted ok. I actually had about 50 thou between the clutch arm and bolt head... Must have set it by the book years ago..... Certainly dont have a coil spring type clutch...

Might give the system another good bleed once Ive replaced the arm.

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http://www.youtube.com/user/Hanras

New clutch arm showed up today via Minisport. Looks like its same width as the original. Ill check this arvy when I get home. Will be interesting to compare the angle of the arm/ball etc up against the original arm. Ill have to get it powdercoted before I fit it, so that might take a while...

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http://www.youtube.com/user/Hanras

I think when I have compared original with new the angle is slightly different, but in a good way if you know what I mean.

Probably done to help bring the clutch point up a little.

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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

Cool. Yeah thats what Im hoping and also the fact the original one could be bent from a million years of use.

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http://www.youtube.com/user/Hanras

Look for wear inside the bearing plunger, where the ball of the arm seats. it's supposed to be a straight drilled hole.
Also be aware that many plungers sold now are soft chinese rubbish- they are made from leadbrite (or similar) free-machining steel and cannot be hardened.
Tip if buying new- if you can file the end where the bearing goes on, it is cheap rubbish. Hardness HRC 3 approx. Should be 50 or more.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I'm with Doc... I always used the return spring until I ditched it on his advice. The clutch has been working fine after several years since....

WRT the to release bearing shuttle... IMHO the condition of the inside bore that the clutch lever sits in is much more important that the shape of the ball on the end of the lever. Indeed a curved flat surface that slides smoothly up and down this bore would be better than a ball.. as born out by the design of the heavy duty arms that you can get from places like Mspares...

I periodically lubricate the ball end by squirting dry graphite down the tube in the release shuttle. DO NOT be tempted to use anything liquid (high pressure grease etc) as that will only attract dust which will soon form a nice grinding paste....

Cheers, Ian

If you're still having problems... it might be worth checking how FAR the clutch slave cylinder pushrod is actually travelling. If you can measure with a small ruler at the end of the push-rod and someone pushes on the clutch pedal, the push-rod should move 19-21mm away from the slave cylinder.
If it doesn't, you are not getting full clutch throwout and most of the other adjustments will be wrong. Overhaul slave cylinder.
Bill

Slave cyl and M/C have just been refitted after overhaul.

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http://www.youtube.com/user/Hanras

What bore is the clutch M/C? It should be 0.75", not 0.70". Some Clubbies had the latter, it does not move enough fluid to disengage the clutch properly. Particularly after years of use and linkage wear here and there. Fit a 0.75" one.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Hahahahaha yeah your right Kev. It's a .700in M/C. Ah well I'll just fit the new arm and leave it as is. The clutch works just right off the floor. It's not like I even actually use the clutch pedal anyways.

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http://www.youtube.com/user/Hanras

Got a new clutch arm, the bloody holes for the clevis pins are smaller at either end..... Seems like pretty hard stuff that arm... How will I open them up? .5mm smaller....

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http://www.youtube.com/user/Hanras

Well the arm is at the engineers. Let them worry about making the holes bigger!

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http://www.youtube.com/user/Hanras