Clutch clearance

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hendy
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Sun Oct 05, 2014 12:37 pm

I'm building my clutch and think I may have a problem..............

When I compress the clutch fully (using a tool rather than the lever), I have around 3mm clearance; this seems way too much, but sticky's only specifies a minimum (1mm). I can't help thinking that if I install my engine with a clutch like this it will slip like buggery.

The other problem is that there is no way that I could squeeze another steel and friction plate into this gap - especially if I were to achieve that 1mm clearance that is needed to avoid clutch drag,

I could increase the gap to 5mm by replacing all my steels with 1mm ones (I have standard 1.5mm ones at the moment), but as a friction plate is 3.5mm and the extra steel would be 1mm, I would be left with 0.5mm clearance, so then I wouldn't have my minimum 1mm clearance.............

Another solution would be thicker steels (say 1.7mm), but I don't think they exist.

Help please

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coaster
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Sun Oct 05, 2014 1:02 pm

1.5 to 2mm is about ideal and you are right, 3mm might cause slippage but probably only on a tuned engine. The top plates can be had in different thicknesses to. I have had to resort to mixing and matching various thicknesses of steels and friction discs to get the clearance right.

hendy
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Sun Oct 05, 2014 1:32 pm

Thanks, that helps, but my engine is tuned (slightly). I have a stage 5 sr 185 cylinder kit, ancillotti clubman, 25mm phbl and varitronic.

Clearly it's not highly tuned, but I'm expecting around 10 to 13 bhp, which while not exactly scary power, it is more than double what it made when it came out the factory 50 years ago.

In a nutshell I need a solution and there isn't one slapping me in the face.

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Angry Bloke
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Sun Oct 05, 2014 2:29 pm

Remember you will able to compress the clutch a lot more with a compressor than with the lever and cam ( when in operation on the scoot) - just check approx how much movement in the plugger inside the chain case when when you move the clutch arm - then tighten the compressor by a similar amount and recheck your clearance

As Coaster says you can adjust the clearance using different thickness steels until you get to 1mm - alway use the thickest steel at the bottom of the stack :D

Hope this helps
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hendy
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Sun Oct 05, 2014 3:44 pm

Angry Bloke wrote:Remember you will able to compress the clutch a lot more with a compressor than with the lever and cam ( when in operation on the scoot) - just check approx how much movement in the plugger inside the chain case when when you move the clutch arm - then tighten the compressor by a similar amount and recheck your clearance

As Coaster says you can adjust the clearance using different thickness steels until you get to 1mm - alway use the thickest steel at the bottom of the stack :D

Hope this helps
En fait, vous etes en erreur. On dit normalement "nous fettlons".

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HxPaul
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Sun Oct 05, 2014 4:50 pm

Sticky's manual only says 1mm as a minimum,this is to prevent clutch drag.If your clutch corks are the correct size-3.5mm thick and you say you are using the 1.5mm steels,there is no reason why the clutch should slip.The clutch springs are a pre determined length and the clutch pressure plate from top to bottom is also a pre determined length.

bazza3004
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Sun Oct 05, 2014 5:47 pm

I built a clutch a while back , it was a standard 4 plate spider and crown wheel but managed to fit 5 plates in by using thin steels an a thinner top plate. This gave me just over 1mm when compressed and no slip on a home tuned imola.

hendy
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Sun Oct 05, 2014 6:19 pm

bazza3004 wrote:I built a clutch a while back , it was a standard 4 plate spider and crown wheel but managed to fit 5 plates in by using thin steels an a thinner top plate. This gave me just over 1mm when compressed and no slip on a home tuned imola.
thanks bazza. i've been looking around on the googlewebs and reckon a good solution is to use 4 x 1.0mm steels plus one additional surflex 2.5mm friction plate - i've only only discovered that they exist in the last 15 minutes

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