Clutch balance question

Mannyroad

Mannyroad

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Hi guys,
I need to know how crucial.is it for the dot and dimple on the hub/pressure plate to be aligned. Why? Because I may have to source another pressure plate for my clutch, and obviously the hub balancing dimple will be useless as it means nothing with a different pressure plate. So, whilst I fully understand the advantages of a balanced hub/pressure plate, is it a no no to swap out the pressure plate.
I ask because I had my hub/pp 'friction surfaces' machined back a couple of millimetres to accommodate an extra pair of plates to help with clutch slip. Unfortunately they've been over machined, so the pp bottoms out on the hub before it loads up the friction plate pack. So I'm going to have to swap out the pressure plate, hence my question.
 
You can see the difference between old clutch and modified clutch in pics (modified on left, obviously). Modified pp needs swapping out for a different one, but then balancing marks are then pointless.
 

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Thanks for your comments guys. Just had other confirmation too, that the clutch doesn't align well unless the dot and dimple align. So what I need to do is check any new pressure plate for fit, by visual examination, ensuring the pressure plate castellations fit freely into the hub castellations and making sure the 'spring sockets' don't bind on the threaded hub bosses.
 
jay760 said:
What's wrong with the one on the left, or am I reading it wrong, 8 plate clutch
Click to expand...
OK, what I discovered when I did check measures was that the 7 friction/6 steels pack measured 32.9mm thick (these are new 3.5mm friction plates, not Heiden's 2.5mm). However when I dropped the pressure plate onto the hub, minus the plate pack, so it was sitting on the castellated rim of the hub, ie bottomed out, the distance between the 'friction surfaces' for want of a better name, was 0.2mm greater. So the pressure plate was bottoming out before the pp exerted spring pressure on the plate pack. So no clutch. However, using my old, unmodified, pressure plate on the modified hub reduced the gap between friction surfaces to 1.45mm less than the plates pack. Perfect. I now have a working clutch AND, importantly, on full travel the pp doesn't touch the casing. And the 1.45mm should give me a reasonable amount of serviceable life in the frictions before it bottoms out. Guess I could, when the clutch plates wear down a touch, put another steel at the hub end of the pack. Get me more life out of the frictions.
 
Last edited:
JOHNDADDY said:
I guess the real concern is if drilling the indexing was a separate operation
how the operator orientated the assembly when they drilled. Perhaps someone with
a couple of baskets could try a swap to confirm.
Click to expand...
I checked my old pressure plate for fit on both the new, bought, modified hub and on my original hub. So long as the dot and dimple are aligned they work in unison perfectly. On inspection, the dot/dimple just make sure you get positioning right first time. Obviously the pp can be placed on the hub every rotation of 60 degrees (6 studs). But the castellations on the hub and pp won't line up properly unless the dot/dimple correspond, because the number of castellations must not be divisible by 6. If there were 30 castellations, or 24 for instance, it wouldn't matter.
 
20220924_190221.jpg


This looks to be the same as the clutch on the left originally a 6 plate so have to use standard clutch plates, need to square off the round corners on the basket so the clutch plate fits as low as possible, the original one that halco copied used to file the corners of the bottom clutch plate so it fitted, the bottom of the thread on the screws need filing back as it is all so close they will cut into the outer basket.
 
jay760 said:
View attachment 327822

This looks to be the same as the clutch on the left originally a 6 plate so have to use standard clutch plates, need to square off the round corners on the basket so the clutch plate fits as low as possible, the original one that halco copied used to file the corners of the bottom clutch plate so it fitted, the bottom of the thread on the screws need filing back as it is all so close they will cut into the
Click to expand...
 
jay760 said:
View attachment 327822

This looks to be the same as the clutch on the left originally a 6 plate so have to use standard clutch plates, need to square off the round corners on the basket so the clutch plate fits as low as possible, the original one that halco copied used to file the corners of the bottom clutch plate so it fitted, the bottom of the thread on the screws need filing back as it is all so close they will cut into the outer basket.
Click to expand...
Haven't fixed off any round corners on the basket. I presume you're referring to the ones at the bottom of the basket cur outs?
I haven't filed the threads at the ends of the screws either and the allen screws aren't hitting the casing on full travel.on my engine. In any event, its not the threads that determine screw head position, it's the long top hat bushes the screws are encased in. But I haven't a problem with this issue.
 
I think I can work out what your doing now, you are using 7x 3.5mm xs1 plates instead of 8x 3mm plates and then taking up the difference with the standard pressure plate
Can you post a picture of the other side of the hub and pressure plate just to make sure you have what I think you have
 
Last edited:
jay760 said:
I think I can work out what your doing now, you are using 7x 3.5mm xs1 plates instead of 8x 3mm plates and then taking up the difference with the standard pressure plate
Can you post a picture of the other side of the hub and pressure plate just to make sure you have what I think you have
Click to expand...
Sorry, can't do that. It's all bolted back up and casing on. The clutch is off a 1980 Special. And yes, I'm using 7x3mm frictions. They are sold by EBC as early Yam R1 plates.
 
The alignment is crucial. Can't remember the maths but it's got to do with prime numbers - of slots in the clutch drum. There's only one way the inner it fits correctly. My bike had been assembled wrong, the clutch didn't work and no amount of adjustment could get it right. 2ManyXS's said he'd never seen one wrongly aligned that worked at all. Because it's a design not balance issue, I would think any clutch pressure plate you buy would have the mark in the right place.
 
Raymond said:
The alignment is crucial. Can't remember the maths but it's got to do with prime numbers - of slots in the clutch drum. There's only one way the inner it fits correctly. My bike had been assembled wrong, the clutch didn't work and no amount of adjustment could get it right. 2ManyXS's said he'd never seen one wrongly aligned that worked at all. Because it's a design not balance issue, I would think any clutch pressure plate you buy would have the mark in the right place.
Click to expand...
Yes, your absolutely right, with all your comments. Having re-examined the hub, there's 29 castellations, so only one way to fit the pp. And yes, that's the same for ANY pair of hubs/pp.
 

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