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MG MGB Technical - 1977 mg b clutch
|just got a new playmate a 1977 mg b love it and have had a few great rides. but it has the most fierce clutch take up i have ever experienced. the pedal is very easy for most of the down stroke then gets hard as heck. with releasing it pushes like a mule with a very short engagement stroke.|
i was told that the slave cylinder was replaced with a toyota or someother part. coul it be that the relationship master cylinder bore to slave cyliner bore is the problem ? the master i believe is an mg original rebuilt part. the cluth it self does not slip, chatter or do anything other than attack my left leg like a gorilla. any advise will be very much appreciated
|It sounds as if you are compressing the fluid in the slave cylinder and lines. Try fitting the original mgb slave cylinder type first and see what happens...|
|What are you comparing it with? Even correct they are noticeably heavier and a bit fiercer than modern clutches. And it is normal for the initial pedal movement to be light and then get heavier, the first part of the travel is only stretching the pedal return spring, then gradually takes up more of the pressure from the pressure plate, until the clutch is fully disengaged.|
If the replacement clutch slave is a larger bore than the original then it will engage nearer the floor and be very fierce, as in both cases the slave travels a smaller distance for a given pedal movement. It should be 32mm bore. Air in the hydraulics (which is what Clive means?) will definitely cause a low biting point, and may make it a bit fiercer. Bleeding is always tricky in the MGB and whoever did it last may have given up before it was fully bled. Proper MGB parts should result in 1/2" to 5/8" of travel of the slave piston for full pedal travel. Last time I did mine I filled the empty system from the slave bleed nipple using a gunson's EeziBleed, which pushes all the air upwards and into the master followed by fluid, instead of trying to push air bubbles downwards. Didn't need any bleeding at all that way. Wear in the linkages at the pedal end will also cause a low biting point but not affect fierceness.
|The correct cyl is easy enough to get so that would be my first job Ted. If it's still fierce it will be oil burned onto the lining which makes them grab or possibly a heavy duty clutch. A new standard Borg and Beck is as light and smooth as most modern 2 litre clutches and better than some due to being hydraulic. Rich.|
|I fitted a new clutch master cyl to my roadster a few weeks ago with interesting results. The clutch had previously been operating perfectly albeit with a slight leak at the main master cyl seals so I replaced the master and expected an immediate improvement due to a new pushrod being fitted as well. Not so.|
Whilst the clutch operated reasonably OK the pedal was very stiff to depress for the final third of its travel almost as if it were releasing the clutch too far. By the time it got stiff it had already released but the pedal still had more than two inches of stiff travel left and it felt as if there was some kind of mechanical roughness when depressing it even with the engine turned off. On checking, the cyl was the correct bore so the only thing remaining was the pushrod. That was certainly the same length and the clevis did not have much wear on it so without removing the master cyl I just took the circlip out and fitted the old pushrod. The result is that the clutch now operates perfectly once more. I've got to admit that I never really did get to the bottom of this one but the biting point is now fine at about 2" above the floor and the very smooth take up which is a feature of this model has now returned.
|intriging ian, were the two pushrods identical?|
could it be a friction thing new tight joint against a used comfortable connection?
i think i wil check nine and possibly oil the joint
and see what happens
|Ted use silicone or red castor grease not mineral oil types near the rubbers. Rich.|
|As far as I could see Ted they were identical. It certainly felt like a metal to metal friction thing. When I examined the original pushrod it was bright on one side as if it had been rubbing on the inside diameter of the main retaining washer at one time. This could happen as the pedal is depressed and the pushrod tips over. That's the only clue that I could find and didn't want to take the whole thing out to check further.|
i have found that the clutch slave cylinder was replaced and the fellow installing for some reason decided that the push rod was to long. he cut it and then announced that it was now a bit to short, but it would be ok, WRONG! does anyone know the length of the mgb clutch slave pushrod. i will endevour to fix this myself. this kind of circus could only happen to me.
but after 18 days of ownership i love my mgb
|I don't have a spare to measure but Moss lists a new slave cylinder pushrod, #180-200 for $12.95 US $. |
|I haven't installed my new slave yet so I can see if I can measure the length of the rod for you.|
|70.4mm end to end.|
I measured an old one that i have, came out of my 67 gt, and it measures 61,5mm to centre of the eye, and 69,5 to end to end.
Did you compare the diameter of the two pushrods? From your comment about the side of the old rod being bright on one side, it might be that the new one is very slightly larger in diameter and binding in the same place the made the old one bright.
This thread was discussed between 05/06/2005 and 19/06/2005
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