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MG Midget and Sprite Technical - 5 Speed clutch conversion despair

Oh how I hate this car, its doing my head in and I am beginning to Despair.

Is it possible Type 9 conversion clutch driven plates are slightly thicker than they should be?

Had problems with new clutch dragging so after a day spent taking all slack out of system and re-bleeding I thought I would give it another try. 1st push of the clutch it was dragging so tried it again. Clutch pedal now solid ( Clutch Diaphragm now gone over centre )? Switched off car and then Bang and clutch pedal back to normal. STRANGE . So tried it again and same thing happened Solid pedal , then bang and back to normal.

So had a look under car and clutch pushrod at a funny angle. It looks that the C/L of the clutch slave is not quite in line with the C/L of the clutch fork. So after 2 actuations of clutch the eye on the fork is twisted. So looks like I will have to take it all out and fit new fork.

So my thoughts are that if the driven plate is too thick it will always drag until its a bit worn, and in trying to cure this dragging I now have too much travel and the clutch is going over centre and then with no more travel available its twisted the fork !
Also pedal is quite heavy don't remember it being that heavy before.

That's my thought any body got any views and ideas.
I AM GETTING DESPERATE

Thanks Roy
R Mcknight

Roy,
I am sorry to say this, but my guess is that you put the clutch centre plate in the wrong way round. Easily done!

Then two things happen, the clutch won't disengage properly, and the clutch pedal stroke is prevented from completing its normal travel and comes up solid. At that point further big-boot pressure on the pedal will inevitably result in bending or breaking something!
Guy W

Guy , I wouldn't be that stupid would I? Or maybe , anything is possible ,its all got to come out so I am almost wishing that's what the problem is. Might of been having a bad day like today. Yep good call Guy

Welcome thoughts from anybody else , sure I read on here that somebody stated they thought driven plates had been supplied slightly too thick and that was causing problems.
R Mcknight

Clutch drag could also be the dreaded spigot bush being too tight on the gearbox input shaft.

Sounds a bit more involved than that though!
john payne

Im not aware of any post that the plate was to thick, only that some are to bigg in diameter...but that was mostly expermential stuff

Prop
Prop and the Blackhole Midget

More likely that the stupid fork mechanisms holes are slightly off line

I had loads of clutch problems using the fork method and the cobbled together angley iron bracket supplied with the kit

Then gave up and now use a Ford concentric setup

because
bill l

Roy
If the clutch rod is at a funny angle do you have the slotted pivot bracket?
There are two types of pivot bracket for the yoke.
1) a pivot bracket with a pivot hole. This replicates the original. If used the guide sleeve on the T9 box over the Imput shaft should be removed.
2) a pivot bracket with a slot. This is used with a roller race that is guided by the retained guide sleeve on the T9 box. The slot allows the yoke to pivot and move through a different arc.

It is also worth checking that the slave cylinder is flat against the Bellhousing as they can foul on the raised leading edge of the bellhousing and not seat correctly. I have also come across an incorrectly drilled bellhousing. I had assumed that they would be jig drilled ? It was not an MMC bellhousing.

If you are using an MMC bellhousing you can see inside the bellhousing through the aperture on the near side whilst a helper activates the clutch.

If using a roller thrust have you forgotten to remove the diaphragm pressure pad?

Alan
Alan Anstead

Thanks Guy and Alan and everybody else who has taken the time to reply.

Let me go through the list of what's what and what I have done and with what and see if any more ideas come to light.

Second hand bellhousing from MMC Birmingham and 2.0 ltr type 9 sierra box.

Fidanza alloy flywheels but checked out exact dimensions to standard 1275 flywheel. Fitted Correct Spigot adaptor and checked fit onto spigot shaft before fitting and lubricated.

Clutch centre plate for conversion from MMC birmingham fitted and tested onto slightly lubricated splines. 1275 pressure plate with Diaphragm pad removed. Gearbox nose piece intact and pivot bracket for fork bracket nicely slotted and bolted up snuggly but not too tight.

1275 Slave cylinder with pushrod 2 11/16 long. Roller release bearing from MMC Birmingham.

So the only 2 queries I have , is it possible the clutch fork I am using is not a 1275 and HOW DO I TELL?

Are all the roller thrusts the same , do any need a spacer between roller thrust and carrier.

When you have done a conversion was the pedal pressure the same with the 5 speed as it was with a 4 speed?

Thanks Roy .. Still Stumped

R Mcknight

Roy
An acquaintance whilst doing a conversion bought a yolk from a Welsh supplier which was bent. I believe it was claimed to be new and that they were all like that. He had to extend the slave pushrod an amazing 15mm.

The part number should be cast into your yolk just beneath the U. Each Spridget engine size has its own yoke.

The pedal should not feel different.

On a couple of conversions it has been necessary to put a small shim between the slave and its rod. Worth a try!

Did a conversion recently where on assembly all was locked. Had to grind back the splines 3 mm as they fouled on the flywheel. The bellhousing / gearbox spacer, of unknown parentage, was found to be 3mm too thin. It was a 1500 conversion so just pointing out that using s/h parts can create problems. Do you know the origin of your yolk?
Sorted the problem only to find the s/h T9 was a dog.

Is it possible that the guide tube over the Imput shaft is slightly too long and fouling?

Alan
Alan Anstead

Have you had the email Roy?
bill l

A photo from a book of the forks. Note there was a production change to the MMC housing that increased the distance from the engine backplate to the gearbox face. Do you have a measurement for this? If the bellhousing is an early one you can experience the problem that is resolved as Alan sugguss by grinding back the splines of the gearbox input shaft slightly.

Daniel Stapleton

Hi Bill , Thank for the photos and Thank you Email sent.

Thanks Daniel , given me something else to consider.
R Mcknight

Daniel , what is the correct fork in the picture . Its a choice of 2 but what one so I can compare when the engine is out .

Thanks Roy
R Mcknight

I believe its the one on the far right which is the fork from the 1275 ribcase box.
Daniel Stapleton

Roy
Just on the off chance
When you pull it apart, check the fit of the clutch plate against the flywheel
I did a conversion on a B once with a Ford box and the metal section of the aftermarket clutch plate that holds the dampening springs was a bigger diameter than the recess of the flywheel. .
There was a row of rivets that attached the steel plate to the lining dampener diaphram spring that contacted the flywheel and held the lining about 60 though away from the flywheel surface giving a result similar to having the plate back to front but not as bad
I took the plate back and swapped it for one that had the rivets on a smaller pcd and all was well
Just a weird option
willy
William Revit

I had a similar problem when fitting a new disc to my Rivergate conversion recently. The current Rivergate clutch disks disintegrate after about 10,000 miles of use. The damper springs are useless Chinese junk and eventually they pop out and lock the clutch cover to the flywheel. This is the second time it has happened under highway conditions, about a year apart.

When this occurs, it snaps the guide tube off of the transmission front bearing cap. I reinstalled the transmission without realizing this and found the fork to be wobbly, the pushrod misaligned and the clutch inoperative. Pulled it all back out, replaced the guide tube and all is well.

I know the Sierra setup is different but Alan's note about the guide tube caught my eye.

I am attaching photos for fun. The failure apparently occurs when shifting from 4th to 5th on a slight grade at 70 MPH. There is no noise or warning, the clutch is simply locked up and dead at the next traffic signal
Glenn Mallory

I walked away in disgust at the thought of pulling engine and box out but been doing a bit of thinking and may have some ideas.
When I built the bellhousing up I tweaked the bracket that holds the clutch fork as it was not putting the roller release bearing exactly in line with the clutch fingers. The knock on effect of doing this means the clutch pushrod was not pushing in a straight line onto the clutch fork.
Now I am using a 2 11/16 pushrod that I believe is wrong as its from a 1098 clutch, should be using a 1275 pushrod that is 3 1/4 inch long. So it looks like the shorter the push rod the sharper the angle it will take up between the slave and the misaligned fork. This has the effect of not pushing in a straight line and in my case it pushes so far out and then due to misalignment it pushes the fork downwards hence the bend in the fork. And with the out of alignment pushrod it seizes up the slave cylinder causing a solid pedal.
So a longer pushrod will work at a straighter angle and exert a more direct push. And a few people have said that even the 1275 pushrod may need spacing out to make clutch work. Clutch pushrod 13H396 from a Mini looks like it will fit and is longer than the 1275 so one is on order and I can modify to correct length and also need to file out slave mounting holes to line up the pushrod with the fork. Just hope this was the cause of my problems . Just needs to warm up a bit in the garage so I can pull out engine again.
R Mcknight

Good luck!

Let us know how you get on

Cheers
Mike
M Wood

Pull the engine out ... agian (gulp)

That sucks, the good news is it gets easier each time

It sounds like a plan, good luck

Prop
Prop and the Blackhole Midget

If you are pulling the box you might to further tweak the clutch fork bracket as the taller it is the less the angle of engagement will be, I think.
Daniel Stapleton

Daniel have you been reading my mind?

Yes its exactly what I have been thinking, machining a spacer to go under the clutch fork pivot to try and get the clutch fork to run at as near to 90dg as possible has to be the way forward. From a mechanical advantage point of view it will take less effort to depress the clutch if the fork pivots as near to 90dg as poss.

Any one done this?

Maybe I wont need a longer pushrod with that mod but just for everybody's info this is the pushrod lengths.

1098 Pushrod 68mm overall length. Part Number 13H21
1275 Pushrod 77mm '' '' Part Number 13H3655
Mini Pushrod 90mm '' '' Part Number 13H396

Roy
R Mcknight

This thread was discussed between 04/01/2015 and 23/01/2015

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