Author Topic: CB750K clutch friction plates with angled slots  (Read 1382 times)

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Offline fxef79

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CB750K clutch friction plates with angled slots
« on: May 07, 2020, 07:39:47 am »
When disassembling the clutch I found the PO installed a friction disk set that has the "angled" cut cork plates, rather than the "square cut".  What I also found is the angles were not all facing the same direction.

When installing these aftermarket friction disk sets, should they all face the same direction?  Which direction is that?

Offline fxef79

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Re: CB750K clutch friction plates with angled slots
« Reply #1 on: May 07, 2020, 08:30:22 am »
FWIW, I believe the general response is going to be "don't use those".  I don't disagree... At this point I'm just looking to put it together as "correctly" as possible until I can replace these later with proper discs.

Having said that, I should ask... what's the recommended new net of discs for OEM/stock configuration?  Let's just call this a
K3 configuration (overall this engine is a Frankenstein, but I've confirmed the clutch hub and basket are "early" style, not the later, i.e. longer, hub that made room for the double-steel disc).  I have 6 single-plate metal discs, and 7 friction discs.  The outer friction disk does not have the larger tabs (the basket doesn't have the cut-out to allow the larger tab).

For example, would the EBC CK1133 be the right set?

Offline Kevin D

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Re: CB750K clutch friction plates with angled slots
« Reply #2 on: May 07, 2020, 10:30:57 am »
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I have just replaced my original square cut plates with the slant cut plates. I have been sitting on the slant cut plates for a long while. I had ordered -300- plates but Service Honda substituted slant cut plates -371-. I recently double checked the part number (at Cmsnl and David silvers??)and found that the -371- is a Goldwing part and has superseded the -300- part. So, having all this extra time on my hands, and being more confident that the part might be OK, I put them in. I have had one successful 20 mile test ride with a few hard shifts, but it's going to take a longer ride and some thrashing to prove that the slip is gone.
 I also visited the GL1000 shop manual and noted from the sketch that the slants are all in the same direction. I don't know, but I'm guessing the GL clutch rotates CCW. The CB 750 clutch rotates CW and I put my plates in with the slants opposite from this GL sketch.
 Noted that the GL1000 has more clutch plates and 6 springs and I'm wondering if that basket would fit in a CB750?
71 CB750 K1
100,000 miles
Original Owner
———past———
70 SL100/125/150
70 Candy BlueGreen CB 750 K0
————————————————-
Former Honda parts kid/counter kid/do all
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Whether you think you can or think you can’t, you’re right
Genius is 99% perspiration, 1% inspiration

Offline fxef79

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Re: CB750K clutch friction plates with angled slots
« Reply #3 on: May 08, 2020, 10:36:45 am »
EBC CK1130 doesn't seem right, seems that's specific to K0.
EBC CK1143 doesn't seem right, that's all "spiral" friction plates ('76 - '78 K).
EBC CK1145 doesn't seem right, that's got the single spiral plate with the larger tabs. ('76 - '79 K)

That leaves me with CK1133.  Which seems right... but I can't just "take a chance" cuz I don't have anywhere else to dispose of the stuff if it doesn't fit (don't know anyone else with SOHC bikes).

Offline HondaMan

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Re: CB750K clutch friction plates with angled slots
« Reply #4 on: May 08, 2020, 06:41:27 pm »
There should be 1 plate like that, on the top of the stack. But, from 2002 until 2006, Honda's parts fiche number was wrong in the published shop manuals (online parts lookups) and they were being sold as all 6 (or 7) of the plates. This makes the clutch slip.

Also: the slots must be 'pinwheeled' out to let the oil slip out, otherwise it holds the oil in and the plates slip. On the 750, as you look at the clutch plate going over the top of the clutch, the slants exit to your left (rear of engine).

The plate thicknesses are often screed up, too, because of incorrect vendors. Measure each plate: it MUST be thicker than 0.128", which is the worn-out lower limit. Modern superbikes use plates that are the same exact shape, but are thinner at 0.127" brand new! This makes them slip...

There should be 7 cork plates in the stack, and the inner face of the top pressure plate should be even with the tops of the clutch fingers. If it is sitting down in the fingers, the stack is too short and thin plates are in it.

The plates you want will measure 0.138"-0.140" thick when new: PartsNmore has the correct ones. You can use one of the slipper plates on the top of the stack like Honda did: this will soften the final closure of the clutch from a stop-to-moving startup. Or, you can install a square-cut cork style instead: take note, though, that this top plate has wider outer fingers than the other plates. It is unique. The PartsNmore version is their part #39-1090 for this one top plate (hint: it was used from 1974 thru the last of the 750, not just the 1976-78 like the parts fiche shows) and the others are #39-1052, you need 6 of these, usually.
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

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Offline Kevin D

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Re: CB750K clutch friction plates with angled slots
« Reply #5 on: May 09, 2020, 06:55:43 am »
Well, you got your answers fxef79, and I have a shaky future with my seven slant cut plates installed:
Quote
This makes the clutch slip
That's what I get for not having The Book on hand. I might give what I have a one season tryout, to see how it does. Or maybe less if it slips badly. I have already missed several excellent riding days due to the invisible menace, parts are harder to get these days, and I hate tossing $100 worth of new parts.
 I got the slant direction correct. ✔️
 I have noted that neutral is much easier to find. Edit👎 one time easy only.
 No clutch slip: ✔️ I got 130 miles on the new clutch, I tried to make it slip, but it was good.
 Time will tell.
« Last Edit: May 24, 2020, 03:51:57 pm by Kevin D »
71 CB750 K1
100,000 miles
Original Owner
———past———
70 SL100/125/150
70 Candy BlueGreen CB 750 K0
————————————————-
Former Honda parts kid/counter kid/do all
—————————————————————-
Whether you think you can or think you can’t, you’re right
Genius is 99% perspiration, 1% inspiration

Offline fxef79

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Re: CB750K clutch friction plates with angled slots
« Reply #6 on: May 24, 2020, 11:24:57 am »
So here’s where I’m at... I ended up with three sets of discs... the slant cut set of 7 that I pulled off the bike, and two square cut sets of 7 - one that was in a parts box that came with it and one that came in a clutch basket/hub/lifter set I bought off eBay (to get the lifter plate). The square cut set from the parts box all measured  0.1385”-0.1400” or so. The square cut set from eBay all measured 0.1395”-0.1410” or so. The slant cut set all measured around 0.1360”-0.1380”. And supposedly this was a “brand new” set that was just put in the bike before I got it.

Note that ALL discs have the same size tabs - none have larger tabs. And my clutch basket doesn’t have the slight cutout at the tip of the slots to accommodate a disc with a larger tab if I had any. I believe it to be a 72 or 73 clutch assembly.

So I’m putting in one of the square cut sets.

I did the oil hole mods on one of the hubs I have and put it all back together.

Now I just need to stop drinking after snapping the tip off the lifter plate. I swear I made sure everything was lined up and seated right. Wtf

Offline HondaMan

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Re: CB750K clutch friction plates with angled slots
« Reply #7 on: May 24, 2020, 02:12:31 pm »
So here’s where I’m at... I ended up with three sets of discs... the slant cut set of 7 that I pulled off the bike, and two square cut sets of 7 - one that was in a parts box that came with it and one that came in a clutch basket/hub/lifter set I bought off eBay (to get the lifter plate). The square cut set from the parts box all measured  0.1385”-0.1400” or so. The square cut set from eBay all measured 0.1395”-0.1410” or so. The slant cut set all measured around 0.1360”-0.1380”. And supposedly this was a “brand new” set that was just put in the bike before I got it.

Note that ALL discs have the same size tabs - none have larger tabs. And my clutch basket doesn’t have the slight cutout at the tip of the slots to accommodate a disc with a larger tab if I had any. I believe it to be a 72 or 73 clutch assembly.

So I’m putting in one of the square cut sets.

I did the oil hole mods on one of the hubs I have and put it all back together.

Now I just need to stop drinking after snapping the tip off the lifter plate. I swear I made sure everything was lined up and seated right. Wtf

Ow! Bummer...wish I could say I haven't done that, though...!
It's real easy to not have the splines at the back misaligned, though, in which case the rear portion isn't lined up, and tightening the bolts down on that is almost 2x the normal pressure, which is the most-common reason it breaks in process. The second-most common reason they break is the use of the wrong springs, like when 4into1 sells someone the springs for the Barnett clutch or the F2/3 clutch instead of the right ones. Those are both longer (and too stiff) for these bikes. And in truth, not needed in those bikes, either... 

Also: if you don't have a wide-finger-tipped basket, you also don't need slant-cut cork plate(s). Unless the basket fits them, there is no reason to mess up the clutch with them, IMHO...
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

Offline Kevin D

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Re: CB750K clutch friction plates with angled slots
« Reply #8 on: May 24, 2020, 04:08:36 pm »
Quote
the splines at the back misaligned

I got a marker and matched one spring tower to the hub, before disassembly.
I drew the spring bolts down as gently and evenly as I could, and was wishing I had the billet lifter plate.

I think it's amazing that such delicate parts can handle the HP and RPM's
71 CB750 K1
100,000 miles
Original Owner
———past———
70 SL100/125/150
70 Candy BlueGreen CB 750 K0
————————————————-
Former Honda parts kid/counter kid/do all
—————————————————————-
Whether you think you can or think you can’t, you’re right
Genius is 99% perspiration, 1% inspiration

Offline fxef79

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Re: CB750K clutch friction plates with angled slots
« Reply #9 on: May 24, 2020, 04:13:49 pm »
I checked the alignment of hub and pressure plate, rotated 90 degrees, tried again, etc., before I put it all together.  Must have done this a hundred times.  Even demonstrated it to my mom when she was sitting in the garage watching.  So I'm pretty darn sure I have that right... but I'm definitely going to have to bend down the tab and take the nut off and really double check it again.  Once I figured it out I marked both with a marker (top of the post on the pressure plate) so I'd know absolutely I had them aligned.  I also test fit the plate without springs and made sure it was able to sit down over the shoulder of the posts.

The one thing I wonder, since you said it, is the springs... I don't know where these springs came from.

Maybe you can help me understand something... I have the shop manual, and your book.  Shop manual gives a number for what they call "clutch spring free length", but not explanation of what that means.  Your book doesn't give a number for that, but you do write about how to check the compression of the springs.  Is "clutch spring free length" the total length of the springs with no load?

If so, I think you might be right... I think these springs are too long.

Offline fxef79

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Re: CB750K clutch friction plates with angled slots
« Reply #10 on: May 24, 2020, 04:15:32 pm »
Kicking myself for not jumping on an ebay item I saw a couple weeks ago... THREE... yes THREE complete clutch sets - baskets, hubs, AND lifter plates... all for $65.  But I was so damn sure... "Ha!  That won't happen to me!  I'll be REALLY sure I do it all correct!"

Gaaah!

Offline HondaMan

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Re: CB750K clutch friction plates with angled slots
« Reply #11 on: May 24, 2020, 07:21:50 pm »
I checked the alignment of hub and pressure plate, rotated 90 degrees, tried again, etc., before I put it all together.  Must have done this a hundred times.  Even demonstrated it to my mom when she was sitting in the garage watching.  So I'm pretty darn sure I have that right... but I'm definitely going to have to bend down the tab and take the nut off and really double check it again.  Once I figured it out I marked both with a marker (top of the post on the pressure plate) so I'd know absolutely I had them aligned.  I also test fit the plate without springs and made sure it was able to sit down over the shoulder of the posts.

The one thing I wonder, since you said it, is the springs... I don't know where these springs came from.

Maybe you can help me understand something... I have the shop manual, and your book.  Shop manual gives a number for what they call "clutch spring free length", but not explanation of what that means.  Your book doesn't give a number for that, but you do write about how to check the compression of the springs.  Is "clutch spring free length" the total length of the springs with no load?

If so, I think you might be right... I think these springs are too long.

Yes, you're right: the "free length" is measuring the spring fully released, like sitting on a table. I didn't put the length in my [final version of the] book because I took out the F2/3 stuff to get it under the 'magic' number of 270 pages. The F2/3 are the longest ones. All too often, though, incorrect springs end up in our modern "clutch kits" because the vendors don't get it right, and some, like for the 500/550 clutch parts, are just trying to Band-Aid the too-thin clutch plates by increasing the spring pressure 150%. These get mixed into the 750 parts supply just because they are "clutch springs"

A brand-new [proper] clutch spring for your bike is 1.25" long. If yours are longer, they are also not for that bike..
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

Offline bryanj

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Re: CB750K clutch friction plates with angled slots
« Reply #12 on: May 24, 2020, 09:56:57 pm »
There are two things that determine strength of a spring
1 length
2 diameter of wire

Many years ago churchill made a tool for checking the pressure required to compress a spring and gave readings for lbs force at a set length and all the old car makers gave readings for it but springs got cheaper and people just changed them instead of checking them
Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!

Offline Kevin D

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Re: CB750K clutch friction plates with angled slots
« Reply #13 on: May 26, 2020, 07:23:59 am »
There are two things that determine strength of a spring
1 length
2 diameter of wire

I put the Barnett springs in 15? years ago. I put them side by side with the stock springs and couldn't make out the difference until I got the caliper out and measured the wire diameter. Sorry, I didn't write it down but the Barnett spring wire was 10%? heavier than the stock springs.

Edit: I did write it down! The Honda springs used 0.100" wire, the Barnett springs were 0.105" wire.
« Last Edit: May 26, 2020, 07:29:53 am by Kevin D »
71 CB750 K1
100,000 miles
Original Owner
———past———
70 SL100/125/150
70 Candy BlueGreen CB 750 K0
————————————————-
Former Honda parts kid/counter kid/do all
—————————————————————-
Whether you think you can or think you can’t, you’re right
Genius is 99% perspiration, 1% inspiration

Offline fxef79

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Re: CB750K clutch friction plates with angled slots
« Reply #14 on: May 26, 2020, 11:11:51 am »
Yes, you're right: the "free length" is measuring the spring fully released, like sitting on a table. I didn't put the length in my [final version of the] book because I took out the F2/3 stuff to get it under the 'magic' number of 270 pages. The F2/3 are the longest ones. All too often, though, incorrect springs end up in our modern "clutch kits" because the vendors don't get it right, and some, like for the 500/550 clutch parts, are just trying to Band-Aid the too-thin clutch plates by increasing the spring pressure 150%. These get mixed into the 750 parts supply just because they are "clutch springs"

A brand-new [proper] clutch spring for your bike is 1.25" long. If yours are longer, they are also not for that bike..

OK, thank you!  I'll be double checking this.  I did find another lifter plate, on the way - along with springs - I'll measure those when they arrive, and compare to what I've got.

Offline fxef79

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Re: CB750K clutch friction plates with angled slots
« Reply #15 on: May 26, 2020, 11:12:28 am »

I put the Barnett springs in 15? years ago. I put them side by side with the stock springs and couldn't make out the difference until I got the caliper out and measured the wire diameter. Sorry, I didn't write it down but the Barnett spring wire was 10%? heavier than the stock springs.

Edit: I did write it down! The Honda springs used 0.100" wire, the Barnett springs were 0.105" wire.

Thank you!  I'll check that against these springs when I get back over to the shop.

Offline fxef79

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Re: CB750K clutch friction plates with angled slots
« Reply #16 on: May 26, 2020, 11:13:45 am »
There are two things that determine strength of a spring
1 length
2 diameter of wire

Many years ago churchill made a tool for checking the pressure required to compress a spring and gave readings for lbs force at a set length and all the old car makers gave readings for it but springs got cheaper and people just changed them instead of checking them

Good to know... hoping to avoid purchase of any one-off tools.

Offline fxef79

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Re: CB750K clutch friction plates with angled slots
« Reply #17 on: May 26, 2020, 11:15:53 am »

Also: if you don't have a wide-finger-tipped basket, you also don't need slant-cut cork plate(s). Unless the basket fits them, there is no reason to mess up the clutch with them, IMHO...

Thanks for the confirmation!

Offline HondaMan

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Re: CB750K clutch friction plates with angled slots
« Reply #18 on: May 27, 2020, 11:46:03 am »
There are two things that determine strength of a spring
1 length
2 diameter of wire

I put the Barnett springs in 15? years ago. I put them side by side with the stock springs and couldn't make out the difference until I got the caliper out and measured the wire diameter. Sorry, I didn't write it down but the Barnett spring wire was 10%? heavier than the stock springs.

Edit: I did write it down! The Honda springs used 0.100" wire, the Barnett springs were 0.105" wire.

This is the difference between the valve springs in the K7/8 and F2/3 engines, too: the F2/3 are thicker, same length. And, they are a bugger to remove with a Craftsman spring compressor! All the other 750 valve springs come in/out easily with this tool.
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

Offline fxef79

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Re: CB750K clutch friction plates with angled slots
« Reply #19 on: May 29, 2020, 04:32:59 pm »
Ahah!  A set of springs was in the box with the lifter plate I received today. Measured them at 1.20” “free length”. BOTH sets of the other springs I have measure at about 1.40”. One of these sets was in it when I got it. So wonder the very tip (not through the hole) was broken on the lifter plate that was on it, and no wonder i broke the other one. Just reassembled with these springs and no problem getting all 4 screws to bottom out. Yes, I think these springs are a bit worn out and too short... 1.20” is at the bottom of the “serviceable limit”... I’ll need to get some new correct springs.

NOW... help!  Can’t find on any of the shop manuals what the torque is supposed to be for these 4 bolts.

Anyone know?  I’m staring at this thing now and I really wanna get the cover back on it and MOVE ON. :)

Offline bryanj

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Re: CB750K clutch friction plates with angled slots
« Reply #20 on: May 29, 2020, 11:23:07 pm »
No torque just nipped up
Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!