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What Is The Correct Clutch Biting Point?


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#1 unburntfuelinthemorning

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Posted 10 November 2019 - 07:15 PM

I've been trying to improve the clutch for ages, it used to drag.  Now after replacing most of the parts it doesn't drag but it does bite very low with engagement occuring as soon as the pedal is released.  So it's driveable but there's nothing in reserve.  Is this where the clutch is supposed to bite or is it still too low?  It's a Borg and Beck clutch, not a Verto.



#2 nicklouse

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Posted 10 November 2019 - 07:27 PM

Adjust it to bring it to where you want it. 15-20 thouโ€ on the bolt is what you need.



#3 unburntfuelinthemorning

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Posted 10 November 2019 - 07:56 PM

I started with 20 thou as per the manuals and have now reduced it to 10 thou which seems rather marginal however there's been little improvement.



#4 nicklouse

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Posted 10 November 2019 - 08:08 PM

Then you have other issues. Wear in the pivot parts. 
 

check what reaver you are getting on the shaft. Should be at least 1/2โ€



#5 unburntfuelinthemorning

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Posted 10 November 2019 - 08:23 PM

I have just over 7/16 in of travel measured at the slave cylinder.  I did have wear in the pins, the end of the lever was worn too but they've been sorted. 

 

The only part left is the master cylinder, I've never changed it.  Is it possible for an master cylinder with an incorrect bore size to be fitted as the pedal feels remarkably light, or maybe I'm just stronger than when I owned Minis before?!



#6 Moke Spider

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Posted 11 November 2019 - 07:32 AM

Pre-verto ?



#7 unburntfuelinthemorning

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Posted 11 November 2019 - 07:39 AM

Pre-verto ?

Yes.



#8 Ethel

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Posted 11 November 2019 - 08:05 AM

Metro masters are smaller bore, but have obviously different reservoirs and a 12x1 pipe union.

Did you replace the plunger along with the arm? If the ball's worn it's likely it's socket has too.

If it was the master, pumping the pedal would likely see an improvement. You could also temporarily wind in the throwout stop to see if that lifts the pedal and help diagnose which side of the wok the trouble lies.

Also, how thick your carpet? ๐Ÿ˜

#9 unburntfuelinthemorning

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Posted 11 November 2019 - 08:55 AM

Metro masters are smaller bore, but have obviously different reservoirs and a 12x1 pipe union.

Did you replace the plunger along with the arm? If the ball's worn it's likely it's socket has too.

If it was the master, pumping the pedal would likely see an improvement. You could also temporarily wind in the throwout stop to see if that lifts the pedal and help diagnose which side of the wok the trouble lies.

Also, how thick your carpet?

Yes plunger replaced.  Pumping doesn't help.  The carpet isn't restricting the pedal travel. 

 

When adjusting, after turning the throw out stop inwards by one flat I can feel the the stop contacting the clutch cover at the bottom of pedal travel



#10 mini13

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Posted 11 November 2019 - 09:48 AM

could the master be stickling partially open/down?  Ive had them stick before but it is normally close to the floor.

 

Also there is a slight difference in the slave bore sizes, but it is only small, 17mm for the verto and 11/16" ( 17.4mm) for the preverto IIRC. but it should be obvious what slave is on there



#11 nicklouse

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Posted 11 November 2019 - 10:00 AM

don't forget to check the master to pedal connection. the MC yoke holes do wear as does the clevis pin.



#12 unburntfuelinthemorning

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Posted 11 November 2019 - 10:28 AM

could the master be stickling partially open/down?  Ive had them stick before but it is normally close to the floor.

 

Also there is a slight difference in the slave bore sizes, but it is only small, 17mm for the verto and 11/16" ( 17.4mm) for the preverto IIRC. but it should be obvious what slave is on there

 

It doesn't appear to be sticking.  Minispares list the plastic bodied GMC1008 and the metal bodied AAU4969 both as genuine AP cylinders a both suitable for either type of clutch.  I have the plastic one.  Don't know if it's AP or not as I didn't fit it.

 

 

don't forget to check the master to pedal connection. the MC yoke holes do wear as does the clevis pin.

There is a very small amount of play in this area but it's so small I don't think it's the problem.

 

 

I seem to lose a suprising amount of pedal travel in taking up the working clearance between the release bearing and the thrust plate even with the adjustment reduced to 10 thou.



#13 nicklouse

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Posted 11 November 2019 - 10:40 AM

you should be able to see how much that is by hand. as in you can pull the lever out till the release touches.

 

it may be that you have the issue that we used to fix by either adding a nut to the end of the push rod or bending the upper part of the arm towards the slave so as to allow the piston to act on the push rod closer to the start of its movement.

 

as you are not really getting enough movement at the push rod. 7/16 is not enough. you really need 1/2" minimum.



#14 mini13

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Posted 11 November 2019 - 11:47 AM

wear at the master clevis is a good call, the clutch arm and master pin, and the clevis pin can all wear and it can really add up.  theres some good info in the below link on the travel at various points of the system.

 

https://www.minimani...FAQ__non_Verto_



#15 unburntfuelinthemorning

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Posted 11 November 2019 - 02:37 PM

you should be able to see how much that is by hand. as in you can pull the lever out till the release touches.

 

it may be that you have the issue that we used to fix by either adding a nut to the end of the push rod or bending the upper part of the arm towards the slave so as to allow the piston to act on the push rod closer to the start of its movement.

 

as you are not really getting enough movement at the push rod. 7/16 is not enough. you really need 1/2" minimum.

Wasn't extending the push rod or bending the arm a bodge when other issues really needed fixing?

 

I only had 3/8" movement when the clutch was dragging so I've improved it by 1/16".  Need to chase that other sixteenth.

 

wear at the master clevis is a good call, the clutch arm and master pin, and the clevis pin can all wear and it can really add up.  theres some good info in the below link on the travel at various points of the system.

 

https://www.minimani...FAQ__non_Verto_

Thanks, I've seen that page before, some good info there, been working through it all slowly.






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