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MG Midget and Sprite Technical - 1275 clutch

Hi
I am running a 1275 engine and box in the frog.
The later 1275 clutch slave has a bigger bore than the earlier 948/1098. I am running the earlier slave which needs an overhaul. I assume the later slave has less movement with a slightly softer pedal. I did have all sorts of clutch release problems originally but by adjusting the pushrod on the pedal box managed to get it to disengage. What have other people done??

Bob
Bob Beaumont

A datsun 5 speed with rivergate conversion could solve your slave cly issues

But then ive always used a 12 gauge pump to kill common house spiders...it works, hahaha

Yeah bob... thats an interest dilima, one thing you might try in making the pushrod/fork adjustable...like in the rivergate conversion kit

It basically readjust the starting point of where the fork starts to engauge

Its basically the slave cly, a threaded rod and a couple of nuts....the threaded rod is the same dia as the old push rod and replaces the push rod then secure the fork onto the pushrod with the 2 nuts on ither side of the fork ....then adjust where the starting position oof the fork begins

About now, your thinking this could be very fiddle and take some time and many attempts to get it correct, to that I say....

YEPP, IT SURE IS...I got the wornout T-shirt as a souvenir

But at least you could experment with differant slaves...or id think you could, someone may prove me wrong

Good luck

Prop
Prop and the Blackhole Midget

Someone should lay off the methamphetamine!
Bob I have a Sebring pedalbox with compatible master cylinder (0.70) on my Sebring rep. It is possible to buy (Brian Wheeler) or make one as I have done in the past. If you are running a twin master cylinder at 7/8 bore it is possible to sleeve down to 3/4 as per 1275.
My 948 (ish) Frog is all frogeye bits, except the clutch drive plate, on a T9 conversion but I have a homemade bellhousing.I prefer compatability to mix and match.
Alan
www.masckent.org
Alan Anstead

Sorry I wasn't being too clear. I don't want to change the gearbox or anything like that. I am going to have to replace the slave cylinder and wondered if the later 1275 slave with the larger 1" bore worked ok(or better)than the 948/1098 7/8" one. I am running the later 3/4" dual bore master.
Bob Beaumont

I just went through this. I have a 1275 in a bugeye.

My master is 7/8 on the drum brakes and 7/8 on the clutch. I started with a 7/8 slave. All parts were new including the forks, pins, and clutch lever pivot bushing. After installation and bleeding it was apparent the clutch pedal effort was excessive. While I wasn't certain it also seemed the travel was excessive and the clutch diaphragm spring was going over center.

I bought a new 1" slave, thinking it would be a simple bolt in and that the smaller slave would reduce the pedal effort and travel. Not so. The fitting on the 7/8 slave is 3/8-24 bubble. On the 1" slave it is 7/16 -20 bubble. The bugeye hard clutch line will not just screw on.

After much searching I found an AN style adapter that will mate the parts. It has a -4 AN male on one end and 3/8-24 bubble female on the other. The nose of the AN end must be shortened (simple filing) and a crush washer used. I installed the parts last week, bled, and just today re-bled the system. The fitting came from anplumbing.com. (part 989541)

The pedal effort is noticeably reduced. It still takes a push, but I think it will be OK. The car is not yet drivable. I no longer have that feeling that the travel is too long. Before I could feel a lightening in pedal pressure as the pedal neared the floor as if the spring went over center.

Posters over on the Spridget forum told me to a) put in a 5 speed, or b) use the correct 3/4 master, lines and 1" slave. I was at the point in the restoration where I was just tired of throwing money at the thing. I decided to use the master and lines I had and make it work as best I could.

Jim
J Scott

Typo above: I meant to say a larger slave would reduce pedal effort.
J Scott

Bob
I understand what you are asking. If you have a 3/4 bore dual master cylinder then the 1275 slave should be the one to use.
Alan
Alan Anstead

many thanks for the advice. I was concerned that the larger slave, even with the 3/4 master would not allow the clutch to disengage as this has been a problem in the past with the smaller slave. I presume the piston in the bigger slave moves slightly less.

Bob Beaumont

The standard 1275 clutch used the 0.7" master cyl along with the larger slave, so the set-up should be correct.
One thing that can happen with 1275 clutches is if the stroke is too long the pressure plate release ring makes contact with the clutch plate when the pedal is fully depressed, causing clutch drag. Paradoxically when this happens you need to lift your foot off the clutch a little to get disengagement - though obviously not so far that it starts to take up again.
Paul Walbran

I am pretty sure that it has been posted here before, but I forgot and can't find it now: what is the correct throw of the 1275 slave cylinder?


thx,
Norm Kerr

Norm Kerr

This thread was discussed between 28/10/2013 and 29/10/2013

MG Midget and Sprite Technical index

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