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Machining Clutch Pressure Plates

Submitted by jack_blakemore on Wed, 23/06/2010
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Commando

Can anyone advise if it is common practice machine down clutch pressure plates?

Thanks.

Submitted by tony_ripley on Wed, 23/06/2010

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Hi,

I don't know about common practice but I did it on mine. These are the phosphor bronze ones and I just increased the inner diameter of the friction area such that the friction area was about halved. My view was that the clutch had been slipping happily every now and again for the last 33 years and showed no sign of any wear on the friction surface so doubling the effective pressure would not do any harm and may do some good. I have done roughly 6000 miles so far and it has not started to slip. It would normally start to slip after 2 to 3000 miles.

I have an 850MkIII with standard chain primary, I use ATF in the chaincase up to the fill level. I do not have any fancy seals on the clutch pushrod.

Are you asking because you have found someone has machined yours or are you thinking of doing it ?

Regards

Tony

Submitted by jack_blakemore on Fri, 25/06/2010

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Tony thanks for the information.

To be honest, no it doesn't look like anyone has machined the pressure plate - that woudl be very difficult to do without leaving obvious machining marks. There aren't any and it looks new.

However someone, an expert in the "larger" Norton fraternity, had been quite adamant that it was common practice - which I have to say I found very odd.

I spoke with Nick of Andover Norton who confirmed that he has indeed seen pressure plates with the wrong part number on.

So the lessons here are: beware the pressure plates - always measure them; beware of any b******t from whoever you may buy 'em off!!

I'll get the right pressure plate and remove the additional steel plate...it might work then.

I'll let you know if the oil seal works - there is good anecdotal evidence to say that it helps.

Submitted by tony_ripley on Fri, 25/06/2010

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Jack,

Sorry, I missread your question. I was thinking you meant the clutch drive plates rather than the pressure plate that the spring rests on.

Is your pressure plate thinner than normal ?

Look at http://www.gis.net/~dynodave/clutchpak.htmthis may shed some light.

I have had my 850MkIII from new and it still has the original clutch plates:-

Body - bronze - steel - bronze - steel - bronze - steel - bronze - steel - bronze - pressure plate. = 5 bronze / 4 steel.

The bronze plates are roughy 0.125" thick, I did buy some new ones from RGM but they are are about .018 thicker so the stack would not go together. They went back.

It was these plates that gave me the idea to machine the friction surface as I mentioned above.

Regards

Tony

 


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