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MG Midget and Sprite Technical - clutch slave pushrod 1275
|We have had problems bleeding the clutch, in that it would bleed, then start playing up again, so tonight I put the car up in the air to see what was going on at the slave.|
I found a significant amount of free play and came to the conclusion that the push rod is far too short. I could literally move the fork back and forth with my fingers with no trouble at all. Push rod fitted is about 6cm long and brand new.
When I went and dug the old one out, it is 10cm long, and after refitting it (even though the hole is severely elongated) the clutch works, but I have to re-bleed as we still get some difficulty shifting, but much much better than before.
So where can I get a 10cm long pushrod new? The shorter one is obviously not correct, I need one for this combination of gearbox and slave.
|Here's a picture of the two side by side
|Hi Dominic, is your engine, box, master cylinder setup original? The reason I ask is I'm 99% sure that my 1275 slave push rod is no longer than 3" and works fine.|
I would have thought that a 10cm one would be far too long.
Do you have any play between the bearing fork and the push rod as the holes can elongate with use.
|on the new rod, huge amounts of play because the rod is much too short, with the old longer rod there is some play, but as the hole is huge and elongated, this is no surprise....|
|According to Moss (USA) there are 2 lengths of slave cylinder push rods used. Moss part#180-200 ( 2 3/8 in.) used with 948-1098 engines, and Moss Part# 180-595 (2 11/16 in.) used with 1275 engines.|
|I had all this bother when I changed the clutch when I had the engine out. I ended up increasing the length of the push rod and then heating and bending the fork until I got the clutch to work properly. It was ok but due to a faulty oil pump I had to have the engine out again. I discovered that the thrust release bearing provided in the 1275 clutch kit was poorly made and had the wrong offset when compared to an original NOS Borg and Beck part. I fitted the Borg and Beck part with another clutch fork and new standard sized 1275 pushrod and put it all back. It bled like a dream and the clutch worked perfectly.|
|slight hijack here. . .when I rebuilt mine I went for the type that is on a bearing, just lately I am having some grumbling noises. . .anyone else had fun and games like this. mines a 1275 1972|
|My 1973 1275 has a roller bearing and also occasionally grumbles slightly. I am not sure that this a problem. Possibly a carbon release bearing also makes a slight contact but the contact wears the carbon and you are unaware of it.|
|There's obviously something not right here, because when I went under the car to see what was going on at the slave, I saw that we still have significant play at the slave, only some of which is dow to the wear in the pushrod.|
SO I removed the bellows at the fork, and could see that there was a LOT of distance between the pressure plate and the clutch bearing. The rubber bellows was preventing the fork from travelling far enough to take up the distance. Once reassembled without bellows, everything works.
But I suspect that the fork is the wrong one. How can I tell without removing the engine again. Where do I get a correct one.
Picture is of the position of the fork at rest after we had got everything bled and working happily, without bellows. I have enough room to get my smallest finger between the back of the fork and the bell housing, so around 6mm
|Dominic, the fork is bent is should be straight!|
|Your forks bent. It should be straight. It is on the new one I fitted to my 1275 gearbox.|
Ahh! Pipped at the post.
They do bend with age.
|Rob aka MG Moneypit|
|yet again a good clear photo has saved the day|
|The usual reason forks bend is owners trying to get a worn clutch to work instead of replacement - not age.|
Longer pushrods fitted to resolve issues often over compensate and just bend the arms with the hydraulic pressure.
Dominic - noticed you have a bolt on place of the normal clevis pin arrangement - assume its a shouldered bolt to give a smooth bearing surface ?
|It is not a shouldered bolt because the rod is extremely worn and this was a quick "see if it works" job. It does, so I will modify a better rod to the same length . There's no point removing the engine to fix the fork until I have to do something else that requires the engine to be removed.|
|The fork muat get quite close to the edge of the gearbox opening when declutching, which probably accounts for why it works better when the rubber boot is removed.|
As the clutch wears the problem will get worse. Can you apply some localised heat and bend the fork slightly straighter.
|if you're not careful one day the clutch could stop working because the arm breaks
|Bob, as the clutch wears the lever arm will move away from the rear edge of the bell housing opening. But having bent that far it could fracture any day soon as in Nigel's photo.|
Of course it does! Dohh
|Are you sure about that Guy? I'd have thought that as the release bearing wears, that end will get closer to the engine / flywheel and as the arm is on a pivot the other end (i.e. the bit outside the box 0 will move away from the engine Towards the rear edge of the opening.|
|Probably right Graeme, for wear in the release bearing. But l thought Bob was referring to wear in the clutch (driven plate), which has the opposite effect.|
|I fitted a Morris Minor roller release bearing on my 1275, and it was so heavy that it gradually fell back from the clutch during clutch-free motoring. Then of course it sort of nodded against the clutch, with little yelps of pleasure. And finally I had to pump the clutch into readiness before using it. |
Good fun - relieved by taking it all out again and substituting the bearing that the set-up was designed for.
|Nick and Cherry Scoop|
This thread was discussed between 04/08/2014 and 07/08/2014
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