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Discussion Starter · #1 ·
Hi guys,

My clutch started slipping. Upon disassembly the top friction plate, closest to the pressure plate, has no friction material left on it and the aluminium has been half eaten away. However the rest of the stack has more and more friction material as you get towards the bottom - almost to the point the bottom one looks new.

I'm not wondering about the slipping part, I've increased the stack back to 39mm with an old friction plate and it's solid again, I got that covered. But my question is about the uneven wear? I'm assuming they should all wear evenly, not just strip one or two plates while leaving the rest progressively good. I've got new plates on order and I don't want the same thing to happen to them.

The current plates, steels and hub are Barnett and were brand new 6 months ago. I've had slippage problems when I first put the clutch in but that was resolved and has been solid for the last 4 months. All friction plates had plenty of material left at that time as well as even wear.

Any idea?
 

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Either the tangs are too tight and not allowing theplates to move freely or the basket is badly notched so the plates can’t float. The whole clutch pack should be able to move in and out with no obstruction.
 
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Discussion Starter · #3 ·
There's a few mm freeplay in the tangs and the basket is 100% so I don't think it's that. You make a good point about the clutch pack moving in and out with no obstruction though. There's no movement with the clutch lever out (of course), but with the clutch lever in, the plates should move freely and not bind. This should be easy to check - I'll update you when I get home.
 

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Discussion Starter · #4 ·
So the top two friction plates are binding with the pressure plate as I spin it with the clutch in. I can only see the top two friction plates though so I cant be certain it isn't just normal clutch drag. It does align with the symptoms so I'm going to go with that for now.

I thought maybe the springs are pushing too hard on the pressure plate, the pushrod isn't fully disengaging and needs extending a fraction, or maybe add another steel while maintaining stack height so the pressure plate slips more freely but engages fine.

I can't reduce the stack height as it's currently 39mm and I first noticed it slip at 37.4mm.
 

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1.6 mm is a lot of wear range from slippage at 37 mm. I think the stack ht. spec for most models is 38.5 or so and beyond that the pressure plate may drag from being too snug. Also , adequate clearance cold may tighten as the clutch pack heats up. Check it when hot to see if this could be part of the problem.
 

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Discussion Starter · #6 ·
So it's taken a while but I think I may have solved it.

I needed to replace the two worn frictions first, the steels had been pretty badly worn too so I replaced them at the same time. When looking at the new clutch plates their diagram showed the stack height as 40.5mm total.

Now with the stack sorted I could move on to the problem. I found this link extremely helpful for pointing me in the right direction Clutch Replacement

What I believe it came down to is I had aftermarket pressure plate springs. Although they measured the same height & within spec I hadn't noticed they were thicker so more force was required to compress them. When installing them I compressed them by hand but could only notice a slight difference. I put the original ones back in to feel the pressure when engaging the clutch, then I used spacers to get the correct pressure in mine. The extra spacers made the springs stick out more so I had to put the rubber seal back on to make enough height for the cover. The clutch is now lighter to engage.

I think that was the problem but it's still early days. I'll have to pull it apart after a few more rides and see if it's wearing evenly.
 

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Every plate should slide in and out of the basket with no drag. Don’t be afraid to get rid of any burrs or high spots to make everything slide smoothly.
 
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