Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: leadnavel on April 27, 2018, 08:29:05 AM
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Any help you guys can give on this would be much appreciated.
I'm part way through a rebuild of my 78 K7 and am unsure if I should reassemble the clutch plates in the order/orientation that I found them? I've read quite a few posts on here and on the US site regarding the orientation of the plates but haven't found an answer. All the metal plates have a round edge and a flat edge and must all face the same direction but as you can all hopefully see from my image the two steel plates below the double-steel plate (the plates in question sit closest to the engine casing if that helps) are flipped to the opposite 'flat edge' direction! Should I flip them to the norm? I have also read on a post that the double-steel plate can be moved to the top of the stack but I can't find the post that mentions the reason for this.
The engine has been sitting idle for 30+ yrs and time has clouded my memory as to whether I was getting problems with the clutch when it was last on the road.
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My experience is with a 500. But my 500 that I'd had for 10 years always had a clutch that came in with a couple of sharp grabs. I had read the bit about the steel plates (but thought it a long shot), so when I rebuilt it last year I noticed that the steel plates were mixed orientation. So I put it back together with all the flat sides of the plates facing the engine. There is also a shim that can be changed on the 500 to minimise clutch basket movement and I changed that. Only the later 550s have the double plate, so can't comment on that.
But the clutch turned out super smooth at the end.
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The workshop manual I have shows it the same orientation as your picture, assuming the last plate to go in place is to the left in the picture.
It gives no indication regarding the steel plates being rounded or square edged and which way they should go at all.
From a techicnical point of view the steel plates all have to interface both sides equally onto friction material, so it wouldn't appear to be altered if they are flipped. The profile just seems to be a remnant of the production process which stamped them out of sheet material. The steel internal teeth don't directly interface with the friction surface, just take the drive from the centre hub.
It looks as if it were absolutely critical they'd have been finished to a matched profile during production.
Maybe someone else is able to shed some light on this.
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Yes K2-K6 the swirled plate is the last one to add to the top of the stack. I have the order right it's just the 'way up' im struggling with, was there a reason why were my plates flipped to sharp side up below the double plate? i'm thinking it was maybe an error by a previous installation! I also read somewhere that the double plate could be located as the top or second steel ring, closer to the swirl plate, for what reason i know not.
While the clutch is stripped down I measured the springs and they don't tally up with the spec for the length of a K7 Spring? The springs measure.
1. 40.02mm
2. 39.84mm
3. 40.20mm
4. 39.81mm
The manual states that K7 springs should be around about 32mm?! Two questions on that. Would this be the cause of my broken lifter plate? What would the reason be to use longer springs?
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The plate orientation I'd feel should be all the same way for the steels, both in front of the double and behind. To me it looks like your front set are correct and you should switch the behind one's to match.
My perception of the reason why is; when the clutch is driving the steel's lugs would be hard up against the clutch hub splines, so to slide the hub through them it would be advantageous to have the "non sharp" side of the plate arranged so that it can't hang up on the aluminium as it is moved with the lever. It'll set it's own position more easily coming back under spring pressure as the plates are effectively floating without drive on them or the opposite affect dependant on how they are mounted.
Spring length, you seem to have F2 springs as they meet that spec. They shouldn't in any way damage the lift plate.
The lift plate damage usually occurs when the four bolts are torqued with something misaligned at the back of the clutch pack. I've seen it assembled with two long bolts screwed into two of the holes and used as handles to jiggle the assembly, making sure it's all in place prior two putting the other two correct bolts in to get and check location. Then, remove the long "handle" bolts, fitting correct one's, and final tightening to reduce this risk.
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You might find one of these a better alternative replacement for the stock item which are prone to breaking?
https://www.ebay.co.uk/itm/honda-cb750-billet-clutch-actuating-hub-Cb750-sohc-1969-to-1978/263157686207?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649
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What would the reason be for the longer F2 springs? thanks for the heads up on the alternative lifter plate sprinta it's nice to have that as a backup!
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The springs just preload clamping force the clutch can exert, but at higher lever effort at the handlebar.
They just expected to F2 to be used more "enthusiastically " than the K7, so as you use alot of revs and launch the bike fast it wouldn't slip under fast starting.
K7 had a more gentle user profile, you'd guess.
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My lifter plate came with an ear pre broken (no sign of the broken bit either), so I replaced it, being careful to tighten the springs evenly, a little at a time, as I understand it they break easily when being tightened slightly on the p*ss.