Idle speed drops when clutch depressed.

[ianh1968]

PS
Mark F, I know you like abbreviations...

How about
"Mini Engines Destroyed" ???

Ian

[carbon]

So is the problem here because the thicker flywheel bolt and keyed washer have been fitted, and are not allowing enough clearance for the clutch cover to release fully?

[ivor badger 2]

I notice that the nipple on the top of the bolt to stop overthrowing the clutch is missing.

How did you get the covers so clean, they look brand new or are they?

[Spider]

If you suspect the washers are in backward DON"T continue to run the engine! You will destroy the crank thrust faces..........

And possibly ruin the crank,,,,

And in one I did see write the block off,,,,,,

[Lakeland997]

Thanks again for giving me further food for thought.

Unfortunately, I'm not able to get back to the car until after the fat man in a red suit has done his rounds. From memory though I think there was about 4 to 5mm clearance between the disc on the cover and the bolt head which I thought would be enough.

Have a great Christmas guys.

[ianh1968]

To check clutch disengagement:

1) Screw it back together and adjust it all up correctly.
2) Remove the starter-motor
3) Remove the spark plugs.
4) Find your favourite assistant.
5) DO NOT START THE ENGINE.
6) Engage top gear and ask your assistant to operate the clutch.
7) If you can turn the flywheel reasonably easily using a screwdriver
in the teeth, the clutch is probably working OK. Bear in mind that you
will be working against the valve springs.

If you can turn the flywheel with the clutch not fully pressed into
the carpet, then even better... (You have plenty of movement).

If you have the hand-brake off and the car moves when the
flywheel is turned, you have a problem.

This is how I check my clutches, but BEFORE I install the engine
in the car. The clutch is activated by slipping a 2ft long gas tube
over the actuation arm and giving it a good heave.

If it works OK like this when on the floor, but not when in the car,
it's either the hydraulics or the mechanical linkage that is at fault.

Ho-Ho-Ho... (etc)
Merry Christmas.

Ian

[coopers1968]

i have a problem with the engine, when pressed i have a sort of roller bearing sound which goes. is this normal for a straight cut gearbox or abnormal, as its a cooper s and i don't wish to damage the engine.
thanks all
merry christmas

[Ronnie]

A little while back we were being supplied Diaphragms in which the centre plate for the release bearing to run on were really soft, it looks like you have one like that. Check it with a file, it shouldn't make a mark on it. The old ones were very hard.

See if you can get a hold of the old style 3W5/8 thrust bearing, they are considerably better than those light duty things. The 3W5/8 are still manufactured and available new, but few places keep them.

As Spider suggests Junk that bearing and use a thrust bearing designed for axial loads! I had one of those bearings fail in the 70s on my way home from London just off the Edgeware Road.

[ivor badger 2]

Thanks again for giving me further food for thought.

Unfortunately, I'm not able to get back to the car until after the fat man in a red suit has done his rounds. From memory though I think there was about 4 to 5mm clearance between the disc on the cover and the bolt head which I thought would be enough.

Have a great Christmas guys.

That should be more than enough. It's just there doesn't look that much in the photo between the plate and the bolt head.

[Spider]

i have a problem with the engine, when pressed i have a sort of roller bearing sound which goes. is this normal for a straight cut gearbox or abnormal, as its a cooper s and i don't wish to damage the engine.
thanks all
merry christmas

(Thanks Ronnie ) Gotta agree with Ronnie here, it does sound like the Clutch Thrust Bearing since it makes the noise with foot on pedal, if it were noise with foot off pedal but goes away with foot on pedal, then I'd suggest that could be gearbox related.

Another bearing I've used with great success (other than the 3W5/8) is a 5203-2RS. It's an industrial type bearing, you'll get these from your favorite bearing supplier. However, they aare not quite a straight out swap type fit. The hole in the Thrust Plate of the Diaphragm should be enlarged to about 20 mm dia (from memory, it maybe a tad more), this is only so that the centre of the bearing doesn't rub on it, though it'll possibly be OK, I just do them to be sure. Don't under-estimate how hard it will be to do this if it's a proper Thrust Plate, it really does take some doing (and this is why I don't fit them to every car).

The other thing is the bearing won't be a press fit on to the plunger, it will be a 'floater' which I don't mind as they self centralise.

I will only use these ^ on the HD applications like, a car that's always driving in lots of stop / start traffic as well as the heavier diaphragams (Grey and heavier). I don't bother with the other (so called) 'proper' thrust bearings.

The 5203-2RS Bearing is a true Double Row Angular Contact Thrust Bearing, the 'RS' refers to it being a sealed bearing (good for river crossings!) not just a sheilded bearing like the stock ones. It's only rated to 10 000 RPMs though, but good for the equivilant of a few tonne force at those speeds. Overkill - yes, but cheap (I pay around $10 AUD) and should last forever.

[migliacars]

I think I had this problem on my racer last few seasons.

Some times it would stall the engine.

Firstly put it in gear engine off. Clutch down. Try starting.
Does the engine not turn as fast as it would when you would try this in neutral. ....

If so sounds like my problem.


I was using med s light weight fly wheel. The cheap one.



A grey diapham. And a med paddle clutch. And steel backplate.
Raced with this for a full season.

When I stripped the engine for inspection the clutch and fly and backplate were all past there best. Not surprising as I'm pushing 220hp now so didn't think so much about it.

Anyway rang med and bought one of there super lite set ups. Alloy back plate new paddle clutch new diaphragm. £600 version. Bolted the complete package on as purchased and the issue I had just went.


so im guess there was some issue with the set up i had

[Lakeland997]

I had a lucky find on eBay and picked up a 3W 5/8 bearing but alas fitting it has made no difference to the problem (perhaps even worse - I can stall the engine now).

IMG_2494.jpg

I noticed that the mark left by the old bearing is quite off centre to the clutch.
Is this enough to cause my issue?

IMG_2508.jpg

I know that there is a cover alignment method detailed in the manual using a special tool and some dowels but I imagine such tools are rare now..
My '78 1275 GT uses a self aligning bearing (same bearing but smaller shaft and a clip to hold it in place) If alignment is the issue, would this arrangement be the answer?

IMG_2511.jpg

[Lakeland997]

Spider's comment about the hardness of the centre discs is confirmed here.
On the left is the brand new disc after a few clutch depressions
On the right is the disc from my 55000 mile 1275GT showing no wear at all
It also appears to have been surface ground on both sides to ensure flatness.
They don't make 'em like they used to...

IMG_2502.jpg

[carbon]

Lakeland,

Did you manage to increase the clearance between the flywheel bolt and the clutch cover release washer?

[Lakeland997]

Lakeland,

Did you manage to increase the clearance between the flywheel bolt and the clutch cover release washer?

I think my original images didn't show the clearance very well. It measures at about 4-5mm.
Here you can see better:

IMG_2452.jpg

IMG_2491.jpg

I couldn't see any evidence of the plate touching the bolt head either:

IMG_2488.jpg

Here's the 1275GT plate fitted:

IMG_2509.jpg

[Lakeland997]

Lakeland,

Did you manage to increase the clearance between the flywheel bolt and the clutch cover release washer?

Also the reason I don't think that's the source is that the engine slows even with very light pressure on the clutch pedal. Seems like as soon as the bearing starts to apply any force at all.

I'm therefore thinking that the problem is either the bearing misalignment or (and I hope not) Spider's original suggestion that I've put a thrust washer in back to front. I have photos that prove the lower ones are in correctly (I can see the tabs) but I can't say for sure the upper ones are right although it would be a schoolboy error and I still can't believe I'd have done that.

I checked the front pulley also today while someone was depressing the clutch and there was no discernible movement. I measured the end float on assembly and it was in tolerance (although regrettably I can't remember the value)

It may help you guys to mention that the engine has steel caps fitted with a four bolt centre and billet crank so the bottom end is far from standard. Everything went together very well however and turned freely as it was assembled.

I'm almost resigned to pulling the unit back out again but if there are any more suggestions...

[Spider]

The grooving of the plate won't be the cause of it slowing (nice easy fix if it were!), however, I'd suggest fitting the old plate back in there (that's what i do with them).

The only things I can think of that would cause it to slow are the crank thrusts (as previously discussed) and the thrust clearance between the rods, crank and the pistons, I tend not to think it's your steel caps, as you'd pick this up at assembly time and if you missed it then, it would bind just about anytime, clutch or no clutch. The other thing is a cracked crank.

Certainly with the 7W5/8 Thrust Bearings, they do last longer when fitted as a floating type, the 3W5/8's don't seem phased.

[mk1coopers]

I've had the same problem with the pressure plate centre being to soft for the bearing, the 'fix' as said was to use an old centre with the grinding marks as they are far harder (though why we are accepting that the new ones are not up to specs rather than returning them until they are put right I don't know)

I would like to run the full face release 3W5/8 bearing in the engine that I'm doing at the moment, so if anyone has a NOS one they want to part with please let me know

[Spider]

You don't have to look (and pay for ) 'NOS' 3W5/8 Bearings.

Just buy a new one as far as I know, they are still made. The Mini Spare Parts suppliers don't seem to stock them though, you'll have to try a couple of bearing suppliers.

Or, if you're really stuck for one, drop me a PM

[mk1coopers]

I'll have a word with the local supplier here, as you say Minispares ect don't have stock at the moment, you may be getting a PM