Topic: Clutch info,please.

[shinyribs]

I know there are a ton of posts on this topic. I have been using the google search on this site for the past 2 days.I have found alot of good discussions about the aftermarket (Barnett & APE) clutches,but the discussions seems to stop short.

I have a '76F and I need a clutch. I can deal with a little more lever pull.Thats not a problem.What concerns me is all the people who have bought the aftermarket kits who either revert back to stock/heavy springs,or just cant use what comes in the kit at all. I have seen some posts where someone bought an APE clutch,and only the springs were useable for him.

I dont want to pay $115 for an APE clutch only to use the springs.

So,what is the deal with the Barnett and APE kits? What works,what doesn't? Do any of them work 'out of the box'? I'm really not educated enough about these clutches to be able to modify/swap out the parts of the kits to make it all work.

My motor is stock but I am working towards getting into some bracket racing. I need a good clutch that will take some abuse. I just want to buy a kit that will work.No mods.

Any and all info/opinions welcome-Thanks,Eric

[HondaMan]

That clutch consists of 6 "square-cut" fiber plates, one "slant-cut" slip plate, 5 steel plates and a double-stacked spring steel plate to allow the whole pack to slip, using the "slipper plate", if you launch too hard. The reason: the first gear is quite tall, and the dogs on gears 1 and 2 (gear # C5 in particular) tend to chip off under heavy clutch action, causing loss of the L shift fork and the C5-C2 gears. This is long history of rhte post-1975 engines.

The fixes:
1. Get the gearset back-cut by APE. This resolves the tendency of the gears to push each other apart and damage things when under heavy throttle.
2. Lose the double-spring plate in the clutch, and the slanted-cork plate. Add one more steel plate in its place, and install all square-cut cork plates. Although Honda's are pricey, they are also the longest-lasting under all conditions, including racing, in my experience - with one caveat: use Barnett springs on those plates. And be sure to EVENLY tighten the retainer plate (each bolt 1 turn at a time - seriously) when installing/loosening, or you'll be buying another one...
3. DON'T use 10w[something] oils, and DON'T use high-detergent oils. Both will make the plates slip and burn the cork. Use at least 15w40 diesel oils (dragracing) or 20w50 motorcycle or Racing oils (longer races) for good results, as these all have lower detergent. Consider using a zinc additive, too, as this raises oil pressure, increases cam lobe lubrication, and makes the clutch plates break friction quickly and grab evenly when engaged. Most oils after 2002 have almost no zinc in them (thanks to the EPA and a crooked politician, but I digress...).

[shinyribs]

Hondaman,thank you for this. I still have a million questions.Even thought you just cleared up a bunch of them for me. From all the info I have been gathering it seems like I will be going with stock parts and good springs.

On that slipper plate,would it be best to reuse that if it I am not having my gears back cut? I understand why it is best to do eliminate this and back cut instead,but I'll have to see if it is in my budget to have them cut first. I really wasnt looking to tear my bike down either,to be completely honest.Also,does that slipper plate slip radially or is it like a cushion that just works within the width of itself...not sure if what i just typed makes any sense whatsoever.Sorry.

Also,where is a good place to find Honda replacement clutch parts?

Thanks again for your help!-Eric

[HondaMan]

That "slipper plate" is the one where the cork looks like a pinwheel. The longer groove between the corks causes the oil to take a longer time to exit the plate surface after you "drop the hammer" all the way, so it gives a fraction of a second of slip before final engagement. This was thought to be a 'shock absorber' of sorts (and it really is such) that would help with the fast wear of the 1 & 2 gears on the post-1975 bikes (F0 and later) with the close-ratio gearboxes. It only helped a little, though: today we see many, many more of these later bikes with the C2-C5 (2nd gear) dogs and slots badly worn, as compared to the earlier bikes. It was probably just a little bit too tall...

In the later years, Honda added sometimes whole clutches made of these plates (and some modern sportbikes are like this), for more cushion. It makes a noticeable lack of snap when dropping the clutch quickly. Some magazines of the 1970s era complained about how sudden the Honda 750 clutch engaged: this also played a part in the change. The hub could not fit more than 7 plates without changing the engine cases, which then would protrude into the rider's foot, so adding the squishy dual-spring steel plate(s) and the slip plate became their solution.

On the CB500, almost all the bikes came with ALL slanted "slipper" plates. These bikes frustrated their owners (I was one of those, as was my brother) when racing on production tracks, because you could never get a good, hard shift. We swapped to the square-cut plates, while some folks tried the Barnetts: this was where we discovered the Honda square-cut plates with Barnett springs were king.

If you get plates from your local Honda shop (pricey, but good quality), be sure to pay for them AFTER they show up, if they have to order them. Their parts system got mixed up in California for a while, and Honda was shipping slant-cut slipper plates as stock plates. I got 2 expensive sets of these, and it took me 5 years to use them up, one at a time... 

BTW: I just discovered today that the so-called "Barnett springs" from APE are much too long to fit the CB750 clutch. Looks like a misapplication: don't get them there...

[MattFreeman]

BTW: I just discovered today that the so-called "Barnett springs" from APE are much too long to fit the CB750 clutch. Looks like a misapplication: don't get them there...

I've gotten three different length springs for my F1. How long is too long?

[shinyribs]

Hondaman,you are a life saver. The slipper plate akes perfect sense now. I noticed on my bike that ,when shifting real fast, sometimes it would pop the front tire up a tad,sometimes it would just feel lazy. I thought it was that the bike was running better or worse on that particular day.maybe that is what I have been feeling all along.

Am I correct in thinking that the spiraled slipper plate is the large one with the wide tang? Are there square palte to replace that one with,or will the standard square plates fit in there just fine.

Sorry for all the questions. I've never had one of the clutches out before and I am trying to get all my ducks in a row for less down time   Thanks again for all your help!-Eric

BTW,I really dig the first line of your sig ;)Good stuff there bud.

[HondaMan]

BTW: I just discovered today that the so-called "Barnett springs" from APE are much too long to fit the CB750 clutch. Looks like a misapplication: don't get them there...

I've gotten three different length springs for my F1. How long is too long?

If you attempt to start the little bolts into the pressure plate bosses and they won't reach the bosses at all: the springs are the wrong ones (too long). This much length can very easily fracture the bolt plate either during assembly or when the clutch gets dropped a little too hard one day. Makes a real mess...

[HondaMan]

Hondaman,you are a life saver. The slipper plate akes perfect sense now. I noticed on my bike that ,when shifting real fast, sometimes it would pop the front tire up a tad,sometimes it would just feel lazy. I thought it was that the bike was running better or worse on that particular day.maybe that is what I have been feeling all along.

Am I correct in thinking that the spiraled slipper plate is the large one with the wide tang? Are there square palte to replace that one with,or will the standard square plates fit in there just fine.

Sorry for all the questions. I've never had one of the clutches out before and I am trying to get all my ducks in a row for less down time   Thanks again for all your help!-Eric

BTW,I really dig the first line of your sig ;)Good stuff there bud.

Yes, I think the slipper ones are slightly bigger OD. They came from the CX500 design (NR500, really). But, you can just drop a standard plate in its place. I would suggest inspecting the dual-steel spring plate closely to make sure none of the little rivets have worked loose. Sometimes they do, and this can make a noisy clutch rattle sound, especially in neutral. If loose, try tapping them tighter on their crimped side with a small hammer and rounded-end punch, or ground off large nail (round off the point) to set the rivet(s) a little tighter. Or, if you can locate one of the GL1000 (1978-79) replacement clutch plate for this one, which was an unsprung, thicker steel plate (one piece), it will also stop the noise and will also add a solid lockup to the clutch. The tiny springs in that dual plate are part of the delayed-grab design.

You might also find an old trick will work to add an extra friction plate overall: reverse the order of the first plate into the stack, making it steel instead of cork. Then, install the cork/steel/cork...stack, using only single-steel plates, losing the squishy one altogether. This can allow room for one extra cork plate overall. Not all of the hubs will fit this: the late K3 thru K5 hubs did, and the F2/3 hubs did, IIRC. I haven't done this in a long time....

[shinyribs]

I never returned to say "Thank you" Hondaman. So....Thank you! This answered all of my questions.Much appreciated!

[shinyribs]

Back with more questions

Ok, for sure, my clutch is toast. My slipper plate was missing a few teeth on one side and ALL of the friction surface on the other side. Just as my luck would have it,the side with no friction material left is the side riding on the aluminum surface of the pressure plate. I could be calling the pressure plate by the wrong name. I really dont know the names of all the parts yet.

SANY0065 by Shiny Ribs, on Flickr

SANY0071 by Shiny Ribs, on Flickr

I tired to get pics of the aluminum surfaces where the friction discs ride.The inner piece has very minute-zero wear on it.Yay! The outer piece (where the friction material SHOULD have been have some Score marks. Nothing severe and only limited to a few very small areas. Can I just dress this area with a veri fine file or something like that?

SANY0064 by Shiny Ribs, on Flickr

SANY0068 by Shiny Ribs, on Flickr

The clutch springs I pulled out measured 1.271" 

The replacement springs I bought measure 1.382"-1.386" 

The FSM says my clutch spring free length should be 1.2575"
   and the serviceable limit is 1.201"
Apparently all the springs I have are too long.

My friction plates measured 0.138"

FSM calls for 0.1347 - 0.1409"  with serviceable limit of 0.122"

So my frictions discs are measuring almost full standard. Are they swollen? I measured a few feeler gauges with my dial calipers and it is measuring spot on,so no worries there. But my discs are really dark. Maybe they should be,I dont know.This is the first clutch I've ever had apart.Oh,the bike has a 42,000 miles on it

Obviously,I need a new slipper plate.Or should I just replace it with a standard friction disc?

Also,are the friction surfaces supposed to ride on the aluminum surfaces? Seems to me there should be a steel plate there

Are my clutch plates stacked wrong?

I know this is alot of questions,but my scooter is down and I just wanna ride Help! I need direction!

Confession time: This clutch was working perfectly fine right up until I started dropping the clutch to do wheelies. So,should I just consider this stripped slipper plate a result of my actions,replace that one part,put it back together and keep rocking? Or should I address the spring issue? Any and all comments please. You cant hurt my feelings

P.S.- Hondaman,the riveted plate you told me about is not in this clutch. Should it be?

[shinyribs]

I pulled the pan tonight and sure enough found my clutch material. The oil pump screen was spotless,but there was a lot of little pieces in the pan.

Are there any certain areas I need to flush/clean other than what is readily accessible with the clutch out and the pan off?

Also,the pieces of clutch out of the pan feel like very hard plastic. Not cork like at all. How should it feel?

Just trying to figure out if I need to replace my whole clutch,or  just the one bad plate, since all of the square cut plates measure well within the serviceable limit. But the brittle pieces has me concerned the whole clutch may be burnt/hardened.

Should I pull my pump apart and clean it? If so,any surprises I should know before tearing into it?

I really dont know how to check these things since I have zero experience. But I just want to learn this clutch,rather than just swap old parts for new. Any advice would be greatly appreciated and helpful. Thanks-Eric


PART_1342581848866 by Shiny Ribs, on Flickr

PART_1342581827850 by Shiny Ribs, on Flickr

[shinyribs]

Ok,I jusr read about facing all the steels in the same direction. Makes sense,but did not know that. So glad I found that. Question: does it matter which way the cut edges face,or only that they all face the same?

[HondaMan]

Back with more questions

Ok, for sure, my clutch is toast. My slipper plate was missing a few teeth on one side and ALL of the friction surface on the other side. Just as my luck would have it,the side with no friction material left is the side riding on the aluminum surface of the pressure plate. I could be calling the pressure plate by the wrong name. I really dont know the names of all the parts yet.

SANY0065 by Shiny Ribs, on Flickr

SANY0071 by Shiny Ribs, on Flickr

I tired to get pics of the aluminum surfaces where the friction discs ride.The inner piece has very minute-zero wear on it.Yay! The outer piece (where the friction material SHOULD have been have some Score marks. Nothing severe and only limited to a few very small areas. Can I just dress this area with a veri fine file or something like that?

SANY0064 by Shiny Ribs, on Flickr

SANY0068 by Shiny Ribs, on Flickr

The clutch springs I pulled out measured 1.271" 

The replacement springs I bought measure 1.382"-1.386" 

The FSM says my clutch spring free length should be 1.2575"
   and the serviceable limit is 1.201"
Apparently all the springs I have are too long.

My friction plates measured 0.138"

FSM calls for 0.1347 - 0.1409"  with serviceable limit of 0.122"

So my frictions discs are measuring almost full standard. Are they swollen? I measured a few feeler gauges with my dial calipers and it is measuring spot on,so no worries there. But my discs are really dark. Maybe they should be,I dont know.This is the first clutch I've ever had apart.Oh,the bike has a 42,000 miles on it

Obviously,I need a new slipper plate.Or should I just replace it with a standard friction disc?

Also,are the friction surfaces supposed to ride on the aluminum surfaces? Seems to me there should be a steel plate there

Are my clutch plates stacked wrong?

I know this is alot of questions,but my scooter is down and I just wanna ride Help! I need direction!

Confession time: This clutch was working perfectly fine right up until I started dropping the clutch to do wheelies. So,should I just consider this stripped slipper plate a result of my actions,replace that one part,put it back together and keep rocking? Or should I address the spring issue? Any and all comments please. You cant hurt my feelings

P.S.- Hondaman,the riveted plate you told me about is not in this clutch. Should it be?

That last picture looks like shows some nasty gouges in the friction surface? That will destroy cork, quick. You might want to get another hub, as resurfacing those costs more than a used hub.

If you have the slipper plate, then there should also be a dual-steel riveted plate in the stack. Those work together.

[shinyribs]

Thank you Hondaman. It does indeed have some gouges. I suppose filing them smooth by hand is a bad idea?

Slipper plate was there,but there was not a dual spring plate like I thought it should(per your previous enlightment )

Will any CB750 hub work,or are there differences?    Thanks once again!-Eric

[shinyribs]

Does anyone have any thoughts or recommendations on my spring free length?

[shinyribs]

I have a set of Honda friction plates coming for the standard square plates. I have 7 of them coming,enough to swap out the outer 'B' plate for a standard Honda square cut plate. It does concern me that the ears are smaller on the 'inner' plates than on the 'B' plate. Should I just go ahead and use the standard inner plate,even though the ears are so small or should I install this 'B' plate? I did not want to go back with an original slipper plate per Hondaman's advice,but was wondering if it would cause trouble using this Barnett plate in conjunction with the other stockers?

I am concerned the small ears will bang around in the slots made for the larger ears and cause it mushroom either the plate or the drum they ride in. Is this concern valid,or do I just need to relax?

$(KGrHqVHJC8E8+3Ul4flBPW4d8oTjQ~~60_3 by Shiny Ribs, on Flickr