T140 Clutch Centre Puzzle

Diving into a T140 engine to check the recent claimed rebuild.
It had obviously had work done but push rod tube leaks meant at least the cylinder head back off to sort. Rockers off showed worn tappets. Head off revealed head bolts all in upside down. So a deeper dive to the sludge trap would ease the mind.
Clutch all seemed fine until I freed the centre...



For some strange reason the bolt heads have been ground down. On closer inspection the inner plate bearing surface and whole clutch centre had all been ground down...
The clutch basket and roller bearings look ok. The thrust washer is worn (the rebuilder didn't bother with a new one)







So, took the centre apart to have a gander



It's been apart recently as there's new rubbers.

 

Looking closer, removing the bolts, they're not correct and odd



The plate threads have been helixed to allow the bolts to fit



The whole assembly has taken a bit of a hammering (which I sort of expect if the repairs are by a lad in the late 70s or 80s armed only with a hammer and a pair of pliers) but everything - bolts, centre and hub have recently been ground down. By a gorilla with a hammer, a file and a grinder.



I'm obviously going to replace everything that needs it. But why carry out the grinding? I can understand the replacement bolts having heads too thick but the hub and centre? Any ideas?

 

The whole back side of the centre has been ground down. The inner plate roller bearing surface (including the marks left by someone digging into it - the red arrows show just a few), the bolt heads, the clutch centre has been ground all the way round - they've even filed a new chamfer around the outer edge and the spider has been ground down to match. The whole assembly is wanked.
I thought for a while that they'd not been able to compress the rubbers enough or that they'd used a mismatched clutch basket but all look ok.
I'll replace it all as the parts are easily available and relatively cheap. Why the dealer didn't do this is a bit worrying but I'll see when I get to the rebuilding stage I suppose.

 

I'm afraid it's been trial and error on my journey of limited knowledge on these machines. I sort of think I know what I'm doing, some of the time.....

I bloody knew I had another one in the stash. Took a while to find it but here's one that I just separated from the basket. See how there's a chamfer on the inside edge. Compare to the next picture. Looks like a skim has been taken across the whole assembly with a file/grinder/cheese grater/chainsaw.





Why would they need to do this? Lots of work with a file for what? Strange, but I expect I'll find out.....

 

I agree, a few measurements required to understand what's been going on. The clutch was a bit stiff but ran very well. I noticed the clutch adjustment access plug had been worn on the inside when it was removed but nothing else seemed out of place.

 

So, this morning I did some comparison measurements between this one and one awaiting rebuild....ground down one on the left, to be rebuilt one on the right



The ground down clutch centre varies in width, across the flats, 1.47-1.48 inches (approx 37.5 mm) while the untouched centre measures 1.5 inches (38.1 mm).
The baskets are different widths (depth of basket) across the flats



But why would someone take depth off of the centre if the baskets were the issue? It must only be the centre protuding too far so I checked the depths to the bearing race



The depths were the same on each. I checked the thrust washer thicknesses - they were the same - and the roller bearing lengths - they were the same.
Then it came to me that perhaps the hub wasn't sitting right on the mainshaft. So I compared the tapered hole in the hubs. The measurements were very close - it's really difficult to measure a taper.
But the gearbox was out so I removed top gear and offered up the hub. The red arrow shows where the hub used to press up to.



Here's the known good hub from the awaiting rebuild pressed on by hand, almost to the line



And here's the hub from the centre that's been ground down



I'm pretty sure this is the issue. The taper in the hub doesn't press on far enough.
Still trying to figure out why the dealer/rebuilder noticed the centre was protuding too far. Maybe it interfered with the primary case. I'll have a look when I'm rebuilding to imagine what a milimetre lengthened centre would do.

Well, I'm pretty sure I know what the problem was now. But I will be checking that the basket and the front sprocket gears line up and will shim the front accordingly.
Always learning.......

 

Agreed that the basket would have been thrown out of alignment due to the taper being incorrect. I didn't check the alignment during dismantle but there was an odd looking shim in there.



Shim is top right. Certainly nothing like any shims I've come across or used before and an odd thickness as well.



Shims I've used are either 10 or 30 thou. This one is 27.5 thou. Which is about 0.7mm. So that could be what they were aiming for.
So why take that off of the clutch centre? It must've been interfering with something.....it's a mysteron. There's no marks on the primary casing from spinning clutch pressure plate or pressure nuts. Maybe the primary cover just wouldn't go on. Or maybe the clutch wouldn't operate with the cover on.
Hopefully it all rebuilds ok with new parts.......

 

Came across another clutch hub today saved from a recent rebuild.



The 'orrible rusty one on the left and the centre one have come off of ex-running engines. The one on the right is the suspect.
Both ex runners are 5 thou bigger diameter on the small end of the taper (the only end I can measure with any accuracy). The ex runners press onto the main shaft further than the suspect one so it's not the mainshaft.
I'm a bit apprehensive but I can't think what else it may be. But I've got to order a new clutch centre (once I get round to it) so we'll see on the rebuild.

 

I think it's solved.
Before ordering a pile of clutch parts I thought I'd use the clutch centre that I already have and dry build the clutch with the existing basket.....
I torqued the centre nut up and the whole clutch was locked solid. The centre would not spin independently.
I dismantled and rebuilt replacing the basket with an old one I have from another build waiting in the corner. It all worked ok.
So, it's the basket. I measured the races in the baskets and all seems ok.
However, when placed flat the race protudes further on one than the other. It's hard to see from the photos but the old race is noticable from the rust pits in it.



While the new one can be seen to be slightly up from the roller bearings...



So, I knocked the races out of the baskets and replaced the older with the newer. Rebuilt and all works as it should. The cast iron baskets are indeed different. When torqued up the centre was pressed against the basket and locked up.

Having been right through this engine now the last builder didn't get into the gearbox or the sludge trap. The sealer used on the cases and innder gearbox cover was the threebond grey stuff while everything else was red wellseal.

As the previous rebuilder didn't get into the gearbox he wouldn't have noticed that the clutch hub didn't get pushed onto the taper of the mainshaft enough and as the clutch assembly was a cheap new one didn't have another basket hanging around so chewed the shit out of the centre to make it work.

Hopefully, it's all been sorted now but we'll see once I get it all back together. Laters ya'll......, over

 

Thanks @Sandi T , muddling on I think is the term. I probably will just go buy new clutch parts but thought I'd have a go at playing with the rusty bits I already have as 300 squids is 300 squids and a bit of filing may well work.
Here's the clutch centre from a 1980 T140E that's been sitting around in boxes. A bit crusty. You can see where the clutch plates have worn into the centre where they bang into the slots. Sitting in the weather since 1985 doesn't help either



It's certainly not as badly worn as I've seen them but the rust on the top I haven't seen eaten into it. Anyway, using a file, started to take the bad bits down to good.



Took the flats down until the slotting was gone. You can see where the plates have worn into the slots.



A right arse getting a file into the slots to get rid of the grooves. The plates really need to slide along this groove or the clutch gets grabby. i.e. the bike moves forward even with the clutch pulled right in.



Once the sides are filed flat then the bottom of the slot is filed.....phew, takes bloody ages....



The rubber bushes were ok, which is surprising as they've been sitting around for nearly 35 years. A bit of cleaning up and finishing off



And the clutch centre can be bolted back together



Obviously the slots are quite a bit wider and deeper than they were so we'll see what effect that has once it's running. Maybe it'll cause a lot of clunking into gear or when the clutch is used but there's not that much more movement when a clutch plate is put in there. We'll see....
Now I have to move onto the basket as it's in a similar state...



Obviously cast in January 1979 but the part number is odd (well, it's actually even) 4642, the parts catalogue shows 4640 up to 77 but later models have no parts number for the basket in the catalogues. I'm sure I could investigate further but hey ho, let's crack on.....



Again, after cleaning and installing the retrieved race that I've replaced in the centre there's a lot of filing to do, ho bloody hum, elbows require more grease.

 

Carried on filing the rust and slots away from the basket until all looked ok



Then to the build up ready to install. Here's the hub (it's taper gets pressed onto the gearbox main shaft when the whole thing is bolted up) and the roller bearings and the thrust washer



Whack a finger full of grease onto the race of the hub and stick the 20 roller bearings on. Count them once they are all on just to make sure. Make sure they are pressed onto the centre as the basket has to fit over them and it's a tight fit.



Plonk on the thrust washer. It's plain metal on the other side so put it this way up as the basket runs against it.



Place the basket over the rollers. This can be an arse to get on sometimes and other times the same one will just slip straight on no bother



Then, not forgetting the clutch spring bolts (those need to be held while the centre is going on - it's a bit fiddly) push the centre onto the hub without displacing anything. This can be a tight fit so have a practice while it's all apart and mark the correct tooth for fitment if it's tight.



Push everything together and while it's being held the basket should spin freely independent of the centre. And this one does......hoobloodyray
Here's the whole clutch assembly ready to be installed



This is a Hyde 7 plate clutch and an alloy pressure plate.