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clutch fork and bearing ID

ozzie alpine

Bronze Level Sponsor
G'day, I'm having clutch problems, still, mostly due to having mismatched components it seems.
Car is an early SII but has been fiddled with, so I am not certain which bits are original.
I need some help ID'ing the parts that I have/need please.
Bottom line is that I may have to replace the whole setup, but I'd like to understand what problem I have before buying more new stuff.

Car was previously working OK for years, albeit with a very heavy and juddery clutch (unknown cover/plate), but I have recently removed that and replaced with a new aussie supplied clutch which is much lighter. This is supposed to be correct for Alpine SII but happens to be 6-spring and 2-dowel so it might be SI, however it should fit...

Main issue at present is the clutch fork, pedestal and release bearing, which do not match the new clutch cover.

Fork has been fitted with a roller-bearing since I've had the car, and if I compare the old bearing to a new carbon one (supplied with the recent clutch kit), it is larger diameter (ie wider lugs), but has the same thickness/depth as the carbon bearing. So the fork has either been modified (widened) to suit the roller bearing, or is off something else. It has some part numbers on it (ie 86124 and 13891) but they don't match any of those numbers in the Parts List. It has a slight bend in it, at the pivot point, but seems straighter than other SII examples I have seen in photos on this forum.
Can someone please advise if my fork looks like a modified original or if its perhaps off something else?

Pedestal is worn and needs replacing or bushing, but it has a part number on it that tells me its a SI part...

I did have it installed briefly last week but the release bearing is very off centre when activating the clutch, causing problems with clutch disengaging and catching internally. The pivot of the fork is all wrong, but I am not sure if its due to the pedestal or the fork, or perhaps a pressure plate that is too "thin", or a mixture of all of these things...

Any assistance welcomed, including supply of new standard SII fork/pedestal if anyone has them?fork2.jpgfork1.jpgbearings.jpg
fork2.jpg fork1.jpg bearings.jpg
 

mikephillips

Donation Time
I don't have measurements for everything but I can tell you that the early SI and II clutch cover was not as tall as the later cover which meant that the pedestal for the throwout arm was shorter in the early cars. And The throwout bearing itself was larger requiring the mounting end ears were further apart. Somewhere maybe in series 3 production, but certainly in IV and V use the clutch cover got a bit taller, used a taller pedestal and a smaller throwout bearing. The new throwout bearing above looks to be the later one. So it seems you may have a mix of parts for the early and later clutch assembly. I'll see later if I can dig out some later parts to get some measurements from to compare.
 

bernd_st

Bronze Level Sponsor
Measure the inner fork opening where the release bearing sits. If it reads around 8 cm you have the proper early series clutch arm. If you have a standard clutch with the center metal thrust ring you should use a standard carbon release bearing. If your clutch cover is non standard pls. post a picture here...
 

jdoclogan

Platinum Level Sponsor
I measured the early fork (I have plenty of these) that came off a transmission with the year 66 casting and late (transmission casting 67 [I have one]) clutch arm. All my early forks have what Bernd described. The mounting post heights are different. Early - 5.6mm and late - 4mm. In addition, the later model has a rather large bearing unit as seen in the photo. The throw to disengage the clutch should be 6mm +/- 1mm. I might add that there was an Australian making good roller bearing units by removing the carbon and machining the holder to receive a pressed in roller bearing. Dave, yours appears to be one of those. I don't know who it is but I would like to know if he has anymore units. Side note from another thread: I have been in contact with TTV Industrial giving them all the necessary measurements to make up a road and track day single plate clutch system. This won't be cheap but may be very usable and high performance for the road or track. They can make double plate system for track only as well (no low rpm performance [like stop and go road cruising]).

upload_2020-4-28_10-39-42.pngupload_2020-4-28_10-40-9.png
 

bernd_st

Bronze Level Sponsor
Was just about to post my comparative picture here ;)


IMG_20200428_202242.jpg

P.S. His arm looks to much straight from the side...
 

ozzie alpine

Bronze Level Sponsor
Thanks guys for your input, much appreciated.
I am still a little confused over early vs late bit, there seems to be conflicting info on small vs tall etc... but we are making progress.

Photo of my 2 clutch covers attached for interest, both have metal centre thrust rings. You can see that the old clutch has an uncentred thrust ring, it also has a broken disc which is why I'm replacing it (rebuilds not available where I live).

Anyway, my fork is 79mm inside, so its an early Series fork. I assume that it is original but I'm still suspicious that it doesn't have quite the right bend.
The release bearing that came with my new clutch kit is smaller, to suit approx 66mm inside fork, so presumably it is wrong, and to suit later series (or something else entirely...).
The lugs that hold the bearings are also different diameter. My roller bearing has 14mm diameter lugs which sit nicely in the fork. The "new" carbon bearing has lugs that are smaller diameter at 12.6mm (ie 0.5") and too small for the fork in any case. Is this a normal difference between early and late series?
Roller bearing is still in reasonable condition and yes I suspect is was made by pressing a bearing into a machined carbon original. Its a good modification in my view but perhaps I should revert to a carbon bearing for the new clutch.

There is a bit more to this story... My pedestal is so worn that the release bearing has significant play and so doesn't engage squarely with the clutch centre thrust ring. This means that the clutch pressure plate was being pushed unevenly, resulting in juddery clutch and there has also been internal impact between the disc plate and the levers on the pressure plate so that the clutch catches before it fully disengages. (see marks in photo) Perhaps the wear in the pedestal has been accelerated because I've been using the roller bearing which is inherently less forgiving? The photo of the new clutch also shows off-centre wear from the bearing - this is probably due to a combination of things - the curved profile of the roller bearing pushing unevenly on the thrust ring due to arc of movement and worn pedestal.

So, I need to replace or bush the pedestal at the very least (were the pedestals not originally bushed?). I need to decide whether to keep the roller bearing, or replace with a new bearing, and I am still of the opinion that (if nothing else changes dimensionally) my pedestal needs to be slightly taller to give me a better arc of movement to operate the new clutch cover, which is a bit thinner than the old unit when bolted up. Is it reasonable to put a thin spacer under the pedestal as a way of fine tuning the optimum arc?

Or, I try to source a replacement fork and pedestal in serviceable condition, its not easy for me to get anything locally or in a timely period at the moment so I'm tempted to try a local fix....
2 clutches.jpg old clutch.jpg new clutch outside.jpg new clutch inside.jpg roller bearing apart.jpg
 

bernd_st

Bronze Level Sponsor
OK, then you definitely have an early fork , but it's messed up and worn. Actually the lugs should have a diameter of around 12.8 mm - no difference between early/late. So your arm has appearantly been widened up. Perhaps even off centre. Would suggest you to drop it and get a better used early arm/pedestal , plus the proper bigger diameter carbon release bearing. Your clutch cover(s) have the matching steel thrust ring.

Regarding the covers: That 9 spring/3 dowels would be correct for a S2. The 6 spring should work as well but thrust and pressure ring condition must be good. You should also measure the pressure ring diameter to make sure it matches the clutch plate.

Another hint: Wonder why your clutch judders and is so much off centre. Can be attributed to the strange release set up but would also check whether the flywheel surface runs true plus that the pilot bearing at the rear end of the crankshaft is there and unworn (brass bushing)...
 

ozzie alpine

Bronze Level Sponsor
Thanks Bernd, thats exactly what I wanted (needed...) to hear. I'll start searching for a fork/pedestal.

You read my mind re. the spigot bearing, I was thinking the same, i'll check tomorrow to see if its worn, but I'll put a new one in anyway.
Flywheel should be good, I had it very lightly refaced recently, but I will do a "run out" test before I put the clutch on.

thanks
Dave
 

junkman

Gold Level Sponsor
You may want to check the flywheel to make sure it is flat. I don't know what type of resurfacing was done, but not all machine shops use a proper flywheel resurfacing wet grinder. Just a thought on clutch chatter.
 

bernd_st

Bronze Level Sponsor
Welcome. Hope you find a good used early fork)/pedestal. This together with the other measures will cure your clutch issues once and forever.

On a side note the carbon ring release bearing does not like to be engaged for longer periods. So don't stand on the pedal @ traffic lights. Just only use it shortly when engaging/changing gears then it will last for a long time...
 

bernd_st

Bronze Level Sponsor
P.S. We just had a case with a club mate where his clutch showed similar uneven wear. After all it was because previous workshop didn't install any whatsoever spigot bearing which made the gearbox input shaft tumble around.
 

ozzie alpine

Bronze Level Sponsor
P.S. We just had a case with a club mate where his clutch showed similar uneven wear. After all it was because previous workshop didn't install any whatsoever spigot bearing which made the gearbox input shaft tumble around.
Spigot bush is a bit worn but not too bad, I don't think it was the issue, will replace anyway.
I have managed to source a good used fork and pedestal, on its way from a very helpful chap in Queensland (thanks Bruce).
Will report back once its installed.
 

bernd_st

Bronze Level Sponsor
Sounds good. Additional hint when installing the carbon thrust bearing:

Put a bit of copper grease onto the dowels and the gearbox input shaft . It will prevent wear and corrosion and ease installation of the engine to the gearbox ...
 

ozzie alpine

Bronze Level Sponsor
Quick update/closure.
All is now well, following replacement of almost everything! I can confirm that reverting back to "stock" SII has resulted in a much better clutch operation than I have ever had.
Turns out that my fork/pedestal were stock SII, but the pedestal was critically worn. Fork was actually OK and serviceable. Thrust bearing now replaced with a standard carbon one.
My "original" clutch cover was perhaps not as stock as I thought; the reconditioned original (also Borg and Beck but different model) now fitted has the centre thrust bearing about 10mm further rearward, resulting in better fork/bearing geometry. The aftermarket clutch kit that I struggled with was rubbish, very softly sprung, poor geometry and could be "over extended" (even though not a diaphragm type), with the pressure plate "levers" interfering with the disc just as it disengaged. Clearly a mismatch of parts despite being sold as a kit.
A frustrating journey but happy with the result, and a big thanks to all here for the advice and to the Sunbeam community in Australia for helping out with parts.
 
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