Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: Paulreade on December 21, 2018, 08:55:18 AM
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Hi guys, I'm after a bit of advice. I have just stripped the clutch down and have 7 friction plates ( existing) 6 of which have perpendicular grooves and the outer disc with the wider tabs has grooves or swirls running out at approx 45 deg. The replacement plates (7 no) all have grooves running out at 45 deg. When looking at the basket from the right hand side of the bike does the basket / clutch spin clockwise ?. If so do the discs fit as per sketch B ?- this would mean the discs would be facing you as shown when inserted into the basket. I assume this is the case as this would allow oil to be thrown away from the plates more easily ?. It's the first clutch I have ever stripped so just want to ensure its put back correctly.d The manuals simply do not show this level of detail that I can see.
Look forward to any pointers / advice / decent YouTube links etc.
Paul
Ps the picture C indicates the pattern of the grooves on the 6 discs removed. The 7th outer disc is similar to B.
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They go in as your picture A Paul
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K6 clutches can be a little complex, first you must make sure it is a K6 basket as, some have been swapped about. The first plate in is a metal plate with the flat side facing in. There should also be a double metal plate ;)
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Crikey pic A ? - surprised at that !. Does the basket spin clockwise ( looking at bike from right side ). The outer (7th) plate on the clutch I removed was I'm pretty sure as pic B so a bit confused now ?.
Can you elaborate on the whys and where fores as to why they should go in a particular direction and what are the pitfalls of placing the 'wrong way'.
There is a YouTube ( the only one I found) by an Aussie guy and he I'm sure placed the discs as pic B , I will however watch again.
In the interim I'd be interested to know the 'tech ' stuff though as I'm on a steep learning curve on this bike.
Kind regards
Paul
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Hi trigger, you mention a double plate , was this the plate to make the clutch quieter that I have heard of, I don't think there is a double plate in mine but I will double check before putting back together. I won't rush this as yet as I'm a tad confused on the disc issue at present. I may photo the existing for comment ?
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Paul. I can't explain anything technical as I go by pictures
Here is the pic and instruction from the Workshop Manual. What I can say is that Trig is rebuilding a CB750 K6 at present, which has an original K6 clutch in it and when he put the plates in, they were as in this picture. Hope this helps a little.
[attachimg=1]
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There were a few different clutches used on the K6, some had the K4/K5 set up and some had the F1 set up.
If you do not have the double plate then, the first plate is a friction pate and build up. All the steel plates have a bevelled edge and make sure the bevel faces out. If one of the steel plates are in the wrong way then, you will get clutch judder ;)
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How interesting. Really appreciate that. I shall try and find out why the grooves are situated as they are and hopefully add a post.
Thanks for your input on this.
Regards
Paul
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Hi trig, nurse Julie.
I think prior to Xmas you asked me to clarify near side or offside. I confirmed offside looking into the basket, which is what the extract you showed on the photo seems to indicate. If that is the case then the friction discs go in as pic A - agreed ?.
I asked the same question on the USA site but no one has replied at all which was surprising, nor has David silvers come back which again is a little disappointing.
Which manual do you use as the ' haynes' manual is far from adequate and quite a disappointment.
If you can just confirm the above I'll get on rebuild. Appreciate your assistance on this.
Regards
Paul
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I can't understand why you asked a question and i gave you the answer and, then you still question my answer :o
In the past month i have built 2, K6 engines and 2, 500 fours which all have the directional plates and lost count of how many over the years. The picture is from the Honda CB500 Four workshop manual, which all plates are directional.
The K6 never really had its own manual but, originally only the last outside plate was directional ;)
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I received a post back from the us site today stating the complete opposite - they referred to a tech bulletin which I have asked for a copy.
It's a lack of confidence issue I guess trig, plus a habit of a working lifetime of clarifying everything with all and sundry before work proceeds. Its all a bit confusing to someone who has never delved into a motorcycle engine before and wants to ensure the bike is preserved for years to come.
:-\
Cheers
Paul
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I think there's information that leads to conflicting opinion on this.
The Honda manual I have for 750 F2 is very specific in stating that the angled slot plate should be fitted as picture B in your early post. it also has the double plate fitted to centre clutch pack.
As far as I'm aware the angle is there to manage oil dissipation as the clutch is released and so will affect the bite "feel" and how smooth the initial drive takeup is. It doesn't look like it will cause a problem as such when fitted either way, but it should change the operation in a small way but only for pulling away from a standstill.
If you look at how the clutch operates, engine running, clutch open, in first gear. Then the metal places are stationary with the fibre plates rotating with the crank, and oil between each interlayer.
As you bring the clutch toward closing then it has to squeegee the oil out of the layers to gain traction and start to rotate the metal plates. This is then driving torque through the gearbox.
As the plate with the angle slots is approached by the flat plates either side of it, the oil has to be wiped into the slot for its exit route out of the clutch pack. If the slots face forward (as in A) then it has the effect of working against centrifuge, which keeps the oil in play longer, which gives a softer clutch bite.
In the B plate scenario, the oil is less retained against centrifuge, so should give a quicker bite transition, and potentially more difficult to modulate torque takeup.
They both don't seem technically wrong but should give subtly different initial affects.
I doubt that the affect is aimed at moving geachanges as all of the clutch pack is moving together after initial pull away.
If you don't like the effect when installed, then it's easy to flip the plate. It's more fine tuning by designers than any technical disaster if it's fitted backward.
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I have always fitted them by the Honda manual, which is in the picture with the 500 four clutch and states " NOTE, Fig 118 " ;)
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Good answer to the question. I will fit as fig A. Keeps everyone happy and makes sense.
Really appreciate the input.
Many thanks
Paul :)
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The other concern is 6 of your plates should be "C" vertical so, it will be interesting to see what the result are as, i have only fitted 6 vertical and 1 angled to a K6 ;)
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Paul, I have just read through all the above, are you certain that the new friction plates you are wanting to fit, are actually for a CB750/4. What I'm saying is, have you ordered / received the correct parts?
Edit...Did you buy this as a kit from David Silver by any chance?
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Hi Julie, I purchased the bike from James H and he sent me the parts for the clutch confirming they are the discs for the bike and from David silver spares.
So hopefully all ok.Do you ask for any specific reason ?
Regards
Paul
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Ah, it's all making more sense to me now. Yes, James did supply you with the correct clutch kit as sold by Silver for a K6. The problem is, maybe it's the wrong clutch for your bike. The kit you really need is from EBC part number CK1145. This kit only has one directional plate. Hope this helps. As you get more used to your bike and the parts, you will realise although David Silver supplies a lot of parts, not all of them are correct, spark plugs come to mind but, that's another story.
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Yes it's been an interesting debate on both sides of the pond ( usa&uk). The guys in the USA have said exactly the same thing that I should be using the CK 1145 pack not a set with all slanted oil grooves. They are also advocating a double sprung steel disc , I guess to quieten the rattle ?.
Will be taking up with David silver spares in the new year.
Regards
Paul
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The bulletin they are referring to is from 'Wrench' and its on here buried right near the end of my dropbox mega CB750 file. It refers to using a double clutch plate from the Goldwing and was used in the Cb750K7 clutch
You need to scroll down a looooong way on this but t's there !
https://www.dropbox.com/s/anpzqn2r55f1o9k/CB750%20Mega%20Parts%20Service%20and%20More.pdf?dl=0
[attachimg=1][attachimg=2]
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I have just had a look on the USA site and Hondaman is correct about the plates but, there is no need for a double plate on the K6 , all you need is a CK1145 and put the final plate in as i have already advised. I have built a number of theses clutches and if it did not have a double plate fitted then, it was built without it and they worked fine.
I don't think you will get any answers from Sliver, they sell parts that fit but, may not work :o Over the years i have had many confrontations with them and all i get is " well, the computer says" >:(
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Cheers trig, do you buy the ck1145 from silvers or just trawl the web for the best deal ?.
Glad I asked the question though initially, it's been an interesting debate.
P
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I get them from EBC ;)
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I can't even find the clutch in my CB750A, hahaha Happy New Year everyone.
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I can't even find the clutch in my CB750A, hahaha Happy New Year everyone.
If you get on to Sliver, they will sell you one ;D ;D
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I might first go down the route that they have sold the wrong one in the first place and ask for an exchange - worth a try
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By way of an update: d avid silver spares unfortunately cannot assist on the clutch issue. They appear to supply a clutch set which comprises of all slanted oil grooves with current part numbers appertaining to the k6 bike. They state Honda made the changes to all slanted friction discs away from the 6+1 set ( 6 straight grooves + 1 slanted grove disc ) and that they supply this for the 'k' series bikes and have had no negative feedback to date.
It's tempting to try the discs before I invest in a ck1145 kit but I have yet to make that decision.
What I have checked is that the friction discs are all well within their service limit ( in fact they are hardly worn at all from the standard values. - leading me to suspect the clutch may have already been replaced. It was biting at around 3/4 which led me to think the clutch was at the end of its life ?.
What I have noticed is that the old springs are way over length. The replacement ( new) springs I have are of the standard length but the old ones are approx 3-5 mm longer - again this leads me to suspect the clutch has been out at some point.
I am tempted to replace the springs with the correct ones and clean all the discs and reuse them for a while longer.
Is this sound logic if the discs are all in spec ?
Also what method would be advised to clean the metal plates before rebuilding the clutch ?, is it a case of brake cleaner and a very light touch with wet and dry ??????
Sorry to rake this up again but it has brought out quite a bit of debate.
The outer friction disc on my clutch was fitted with the outer edge of the grooves trailing the inner, I will flip this as per triggers advice and have the inner edge of the groove trailing the outer as per the attached to see what effect this has ?
Regards
Paul
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If Honda made changes to all slanted plate then why are Sliver doing this kit as 1 oem and 6 aftermarket friction plates ???.
Clutches can be a little strange and i would not believe the Honda service limits. I have had shed load of clutches slipping and on removal of the plates, they have been with in spec. New friction plates in and everything was working as it should. A plate can be with in spec but, if it is old and brittle it will slip.
There are two different lengths of springs fitted to the 750's. Make sure you have a K6 clutch basket, just because your bike is a K6 it, doesn't mean all the parts are K6 ;)
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Duly noted trigger, ck1145 required.
Plot thickens as regards the basket query ???. Would it be too much trouble to throw a few pointers to see if I can clarify if it's a k6 basket ?.
It's the first basket I've ever touched - let alone identifying it's type ?.
Is there a specific thing I can check or would you need photos etc ?
Many thanks
Paul
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I would just fit the CK 1145 and the spring that came out your old clutch basket. The shorter springs can be a bit of a bugger and i think they maybe a supersede part. Check the PN of the springs against the original PN for the K6.
Have not had time to look for a K6 basket and take photo's as yet.
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Here you go! A K6 clutch and i have put a picture of the different springs ( both OEM ) and a clutch plate that has gone hard and brittle.
[attachimg=1]
[attachimg=2]
[attachimg=3]
[attachimg=4]
[attachimg=5]
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Thanks trigger, on the face of it looks very similar but will brave the cold in the garage and compare later.
On the springs I want to fit the shorter new springs - can you see advise if you for see a problem with that at all ( from memory they measured 32.7 mm as opposed to 35mm for the removed Spring)
Clutch plates ( new ck1145) have been in soak overnight ready for install.
Many thanks
Paul
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The longer spring with give a smoother operation and a better lever ;)