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 Post subject: flywheel set up question
PostPosted: Sat Aug 19, 2017 12:57 pm 
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998cc
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Location: Airport West
I have a question ....there's a 66 thou gap between my drive straps and the lugs for the back plate. Calver ST states I should remove the gap between them by machining down the spacers under the drive straps on the flywheel but in my head I'd need to make long spacers off the backing plate ....... thoughts ?
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PostPosted: Sat Aug 19, 2017 1:08 pm 
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998cc
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Nicked from the Calver st web site .....

"Clutch - Drive strap alignment & diaphragm assembly
If the pressure plate clutch plate friction face needs re-surfacing, get it machined to clean it up. Make sure the engineering company doing the job records the amount taken off as once done, the recorded amount needs removing from the tops of the 'horns' that stick up to ensure proper clamping force is achieved. If this is not done, clutch slip is inevitable. If using a pressure plate of unknown history, it is IMPERATIVE the clutch drive straps are set at the correct height. Many get this wrong and end up with a slipping clutch for some seemingly unfathomable reason. The following should also be carried out if the flywheel has been machined, or of unknown history also:
- Place the pressure plate 'horns' upper-most on something to hold it off of the work surface but not interfere with clutch plate or flywheel
- Place the clutch plate in position, with the protruding primary gear spline boss on the underside facing the work surface
- Place the flywheel in position
- If the drive straps are holding the flywheel up, or are under tension pressing on the pressure plate 'horns', more spacer-washers/shims are needed between the drive straps and flywheel
- If there's a gap between the drive straps and pressure plate horns, the spacing between the straps and flywheel needs reducing
- If no drive straps are fitted, using a straight edge or drive strap fitted to one of the horns, measure the existing gap between flywheel surface and underside of straight edge/strap, and make suitable spacers to this measurement
- Where extra drive straps are fitted, as in racing (3 on each location instead of the original two), it is essential to machine the thickness of the drive strap off of each pressure plate 'horn' and spacer to re-gain correct diaphragm clamping action to avoid clutch slip

The idea is to set the straps so that when they are in their 'as assembled' position, they are not under tension, nor are well clear of the pressure plate horns. They should be JUST touching. Under tension the clutch will slip due to decreased clamping pressure. Too far clear may cause disengagement problems. "

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120bhp with 450kg just fun waiting to happen

We were prob. drunk when we set it up last and thought this will be a good idea


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PostPosted: Sat Aug 19, 2017 7:30 pm 
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998cc
998cc

Joined: Sun Nov 06, 2005 5:41 pm
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Location: Adelaide
Should this be checked with the diaphragm spring in place, as this will pull the pressure plate up, crushing the clutch plate, and changing the "clearance" for the straps.
With the diaphragm spring in place you can't check the clearance, but you see if the straps are straight.
Wrongly or rightly, this is how I checked mine.


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PostPosted: Sun Aug 20, 2017 10:18 pm 
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justfanginaround wrote:
- If there's a gap between the drive straps and pressure plate horns, the spacing between the straps and flywheel needs reducing


this is you, right?

reduce the gap by what ever way works, but machining the spacers (or making new) is the smart way to do it as you're not adding washers or anything that can lead to another point of failure

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Should this be checked with the diaphragm spring in place, as this will pull the pressure plate up, crushing the clutch plate, and changing the "clearance" for the straps.


I don't think the clutch plate crushes... I think I'd be worried if it did, it's all riveted together... :?

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PostPosted: Mon Aug 21, 2017 7:30 am 
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Diaphragm spring should be flat when it's all assembled. I sit a 3mm drill on the spring, if it is parallel to the flywheel it is correct. If not, assemble with only 3 straps and check again. Each strap is .035" thick, this will help show how much needs to be machined off the 3 backplate lugs.

See http://www.minimania.com/Clutch_FAQ__non_Verto_
For more information.
Worst case I've seen they needed .070" off. A result of flywheel and backplate refacing over the years without facing the lugs to suit.

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