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MG Midget and Sprite Technical - Clutch cylinder bore sizes 1275

I have an Aussie built 1969 Mk3 1275 midget.

Can anyone confirm the bore sizes I should have in the clutch master cylinder and corresponding slave cylinder please ?.

Thanks in advance,


The slave is 7/8" and the master 3/4"
Bob Beaumont

Thanks Bob, much appreciated.

1275 is 1". 7/8 is the size for earlier Midgets.
With 7/8 on 1275, there is too much travel of the clutch arm, which overstresses the diaphragm and shortens its life. It also can cause the releas ring in the centre to make contact with the centre of the clutch plate, causing clutch drag which feels as though the clutch isn't disengaging properly. (Don't ask me how I know!)
This results in a counter intuitive situation where you need to release the pedal a bit to get the clutch to disengage ...
Paul Walbran

OK, having just fitted the overhauled slave cylinder tonight, and getting a good pedal first attempt (no air bubbles !), I will knock off the dust cover in the morning and check the bore size.

The travel at the clutch lever was about 10mm with the clutch pedal fully on the floor.

The master cylinder swap is on Saturday - I will check the bore on it too and report back.

Interesting. I have the earlier 7/8" slave cylinder on my 1275 frogeye mated to a later 3/4" bore master. It has performed well for years without any of the problems described.
Bob Beaumont

This thread was discussed between 17/04/2013 and 18/04/2013

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