Topic: 836cc Power is Way Too Much Due to Some Very Bad Advice

[HondaMan]

One thing comes to mind: I just bought a set of Honda's own plates and am VERY disappointed (including the price: yours were WAY cheaper than mine!). For many years, theirs has beat the Barnetts, period, in every way, and it would tell the most in racing. But, this new design is very, very different from the old ones I know.

The original plates have square (rectangle, really) corks on the friction plates, and they are all planed to a very even, rock-square vertical profile, too. These new ones are shaped like the notorious 500/550 slip-plate corks, slanted into a rhombus. To make matters worse, the corks are not rock-square, but curved to a "mound-in-the-middle" shape, all of which will seriously reduce the grip surface. I am afraid to install these in my warmer-than-stock K2, because I know I will suffer just what you have: slip. The surface grip area is only about 60% of the existing plates.

This is sad.   

I may have to find some way to modify Barnett plates, by prefacing and polishing them - or something. I don't like them: their fibers end up inside the oil pumps, never a good thing.....

[MRieck]

Hmm, I'd forgotten I had that trouble with the clutch. I guess it's a perfect time to report that even with lots more motor than before - the stock, Honda fibers and steels work perfectly using the heavy Barnett springs. I've not had one hint of it breaking loose and the clutch pull is still very nice. It's a firm pull, but the Honda design handles it perfectly.

Honda steels +Honda fibers + Barnett springs = happiness under a lot of pull.

Thanks to those steering me into the light on this one.. Gordon

 

That is the set up I use. It works perfect.

[Bodi]

I doubt if you can make Barnett plates work. The friction material seems to be the problem. Like you say, it wears quite rapidly blackening the oil and although I haven't looked in the pump I found a lot of fiber gunk in the oil pan. I tried cutting channels in the "corks" with a mini hacksaw to try and reduce the cold lockup, it didn't help appreciably. I have a 400F (Barnett 350 twin kit) and a 750 Barnett pack somewhere in a box if you want to try.
On the 750 (as I recall it had an 800cc kit , cam, and head work - not my bike) and 400F (466 kit, cam, headwork) I used stock Honda internals and Barnett springs, good left hand exercise but no slipping. Both slipped with stock (in spec) springs - the 750 owner had switched to Barnett because of slipping which of course cured that but he was tired of the morning ritual to try and declutch the bastard. I did have to clean his oil pump to get the backflow valve working but it never occurred to me that clutch crap was clogging it.

[Jerry Rxman Griffin aka MuthaF'er]

Hey guys,

I'm not at home to check this out but doesn't the Barnett kit come with 1 extra plate to accomodate all the years? Remove 1 plate before installing on certain years?

My Barnett seems to work great but it's been in the bike (75 750F) for some time and I don't remember how I installed it. I think I have 1 spare disc in a box in the basement.

[Big Jay]

The CB rips the clutch loose at 7,000 rpm since I installed a $200 NOS Honda stock clutch - Darn it! I just got it back together last night and my 1st ride greets me with a quick sweep of the tach needle past the 10 mark....

I made use of some bad advice while I had my 836 down for the frame mods. I had installed a new Barnett clutch fiber plate and spring kit back in August when I was putting the engine back together. It worked extremely well in terms of "grab". In fact, it worked too well and caused jumping when put into 1st and I'd had a few false neutrals show-up when going through the gears. A local friend and long-time CB750 owner told me he'd drag raced his previous 750's and used only "stock Honda clutches" without ever having one slip or problems. He insisted that he hated Barnett fibers because they would swell more than the stockers and cause the "sticky" transmission problems I was having. He also insisted the stock clutches on the CB750 worked so well that a new set of stock Honda springs would be all it needed.

Well, the engagement to first is clock-work perfect, the shifting is as smooth as any bike I own. This morning I'm really happy about taking advantage of his advice and the expense of replacing a new Barnett system with less than 200 miles with the outrageously expensive Honda fibers (those 7 fibers are $18 each! and the steels are $8). I'm happy for a good 20 miles or so. I come to a stop sign, look down and the oil gauge shows a drop in pressure, so I know she's warmed-up and the oil has thinned a little - all good. I click into 1st and hammer it once rolling fully expecting it to hoist the front tire like it's done so easily for the previous 200 miles. Nope, not this time.

A bad clutch usually shows it's ugly head in the higher gears. This damn thing is so weak that it's won't handle the 836 in 1st. I loosened up on the adjuster making sure to give the cable 1/2 of slack and brought the rpm up while in 2nd so I could watch it. At 7,000 shes starts and before I can get out -she tachs over 10,000. While I am just tickled at the output, I'm not happy at all about having to replace more clutch components.

Question - I like the shifting quality and love the way my transmission behaves with the Honda fibers/steels. Will a simple swap to heavier springs solve this? I don't want to go back to the Barnetts, but 10 grand on the old tach will soon open a few windows on the frontal case areas...

Input really appreciated.

Thanks,
Gordon
 

This is why we developed the 9 plate clutch back when we first did the big Hondas. You can not slip it with your 836.



http://cbrzone.com/clutches.html

Jay

[sandcastcb750]

I am sort of confused by this discussion...........I have experienced differently.

First, I have a 836cc and a Barnett clutch. Clutch works fine with this combination.

When I had a stock Honda clutch, it lasted 500 miles and I didn't even ride the bike that hard. After 1000 miles the clutch was like a torque converter on an automatic. As soon as you give it the gas, the rpms increased wildly. I could not go over 70 mph because the engine revved as the clutch slipped.

After the Barnett was installed, the clutch worked perfectly. When into neutral with no problem. No slipping.

With regard to the clunk into first gear, every CB750 K0 to K5 did it; the earlier models seemed worse. My K8 was better as I remember. Just a nature of the beast.

Probably an extra disc or plate would help.

[MRieck]

I am sort of confused by this discussion...........I have experienced differently.

First, I have a 836cc and a Barnett clutch. Clutch works fine with this combination.

When I had a stock Honda clutch, it lasted 500 miles and I didn't even ride the bike that hard. After 1000 miles the clutch was like a torque converter on an automatic. As soon as you give it the gas, the rpms increased wildly. I could not go over 70 mph because the engine revved as the clutch slipped.

After the Barnett was installed, the clutch worked perfectly. When into neutral with no problem. No slipping.

With regard to the clunk into first gear, every CB750 K0 to K5 did it; the earlier models seemed worse. My K8 was better as I remember. Just a nature of the beast.

Probably an extra disc or plate would help.

The Barnett springs eliminate slipping. The Barnett clutch material was a problem and not just for CB's. I've always used OEM Steels and fibers with heavier springs or a conversion kit to eliminate a diaphragm spring. I have also used cryo aluminum plates in a handful of bikes with mixed results.

[mrbreeze]

I can appriciate these discussions about what friction,plates and springs work for everybody but nobody is mentioning what kind and weight of oil is being used or what temp,type of terrain, etc. My clutch slipped a few times last year but people said I should use 20-50 Castrol.Diesel oil,or cycle specific oil instead of 10-40 Castrol automobile oil.I will be going with the 20-50 Castrol and my new oil cooler from Terry and hopefully....no more slip.

[nickjtc]

I will be going with the 20-50 Castrol and my new oil cooler from Terry and hopefully....no more slip.

Castrol is the shiznit. There, I learned a new word today!!

[Sam Green Racing]

I can appriciate these discussions about what friction,plates and springs work for everybody but nobody is mentioning what kind and weight of oil is being used or what temp,type of terrain, etc. My clutch slipped a few times last year but people said I should use 20-50 Castrol.Diesel oil,or cycle specific oil instead of 10-40 Castrol automobile oil.I will be going with the 20-50 Castrol and my new oil cooler from Terry and hopefully....no more slip.

What clutch have you got in it Freddy.

Sam.

[sandcastcb750]

Mike- I agree heavier springs would be better. Maybe that's all it takes to fix the problem.

[mrbreeze]

I can appriciate these discussions about what friction,plates and springs work for everybody but nobody is mentioning what kind and weight of oil is being used or what temp,type of terrain, etc. My clutch slipped a few times last year but people said I should use 20-50 Castrol.Diesel oil,or cycle specific oil instead of 10-40 Castrol automobile oil.I will be going with the 20-50 Castrol and my new oil cooler from Terry and hopefully....no more slip.

What clutch have you got in it Freddy.

Sam.

Sammy.....my clutch is butt stock far as I know. I have never changed it. I am going to run an experiment this season and just try the 20-50 oil. If it bites better....great.If not....I'll be shopping(again!)

[Sam Green Racing]

Hi Fred, if your plates are all in spec, stick a set of the stronger springs in and use the right grade of oil for the temprature you ride in making sure it is motorcycle oil and not motor oil.
You should be ok with that.
Good luck Freddy.

Sam.

[rangelov]

If I recall correctly...  An old trick was to use CB450 twin clutch springs.  There were much stiffer than the stockers in the CB500s.  My Old CB500 (550cc with Yoshimura kit).  Would slip a lot.  Bought the  CB450 springs, but never got around to installing them.  But they were more spring than the CB500 four.

Can someone confirm that these springs will work in CB750s and add more clutch force as well?

[Jerry Rxman Griffin aka MuthaF'er]

Be careful with changing springs. The "kids" at the Honda dealer sold me the "correct" springs and I had problems. They might have been correct but not for my bike. The ones I received were either longer &/or did not compress as completely as the stock set. When the 4 bolts on the plate were tightened down (even used my torque wrench) a corner on the plate snapped off.

[seaweb11]

Be careful with changing springs. The "kids" at the Honda dealer sold me the "correct" springs and I had problems. They might have been correct but not for my bike. The ones I received were either longer &/or did not compress as completely as the stock set. When the 4 bolts on the plate were tightened down (even used my torque wrench) a corner on the plate snapped off.

There is more than 1 reason why that can happen.

[eurban]

Be careful with changing springs. The "kids" at the Honda dealer sold me the "correct" springs and I had problems. They might have been correct but not for my bike. The ones I received were either longer &/or did not compress as completely as the stock set. When the 4 bolts on the plate were tightened down (even used my torque wrench) a corner on the plate snapped off.

There is more than 1 reason why that can happen.

Absolutely right!  If you do not tighten the bolts in an even manner the posts on the pressure plate will not seat properly on the lifter assembly and things will bind.  Keep on tightening and the lifter's ear will break.  Also if you do not mesh the teeth of the pressure plate plate properly with the clutch center then again the pressure plate towers will not be able to seat on the lifter and you will break an ear.  You can mess up this engagement by having the center and the pressure plate out of "sync" by 180 degrees (the teeth will not line up this way at all) or even if you have them oriented correctly if you do not pull the pressure plate forward and engage it with the teeth while you are beginning to tighten the bolts then it may not necessarily self engage as the spring tension is increased.   Bottom line is that the posts on the pressure must physically touch the the lifter when you are done tightening the bolts. When you get metal to metal contact the bolt will then be tightened to proper torque.  These are fairly common pitfalls and the manuals typcially suggest marking the center and pressure plate for proper orientation prior to dissassembly.

[HondaMan]

If I recall correctly...  An old trick was to use CB450 twin clutch springs.  There were much stiffer than the stockers in the CB500s.  My Old CB500 (550cc with Yoshimura kit).  Would slip a lot.  Bought the  CB450 springs, but never got around to installing them.  But they were more spring than the CB500 four.

Can someone confirm that these springs will work in CB750s and add more clutch force as well?

As long as the inner and outer diameters are similar and the compressed height of the springs mathc, many different springs will work, giving different characteristics along the way. The Barnett "system" used to consist of springs with 10% stronger spring wire and plates that had their higher-friction cork material. Over the years, I have seen Barnett's springs on stock Honda plates in many roadrace bikes and some of the non-turbo drag bikes of the 750 genre. There was a time (is it still?) when you could buy the springs separately. With the situation we're seeing now, my first reaction would be to try the Barnett springs with these new Honda plates to see if it helps.

Another thing to remember: if the plates are not well-oiled, they burn out very, very quickly, typically in less than 200 miles. The heat glazes the face of the cork and then cracks it, making it crumble right off in little pieces. In the 1960s and 1970s, the Barnett plates came in plastic bags marked "soak in oil before use" with a little sticker for the bikes I serviced (Honda, Suzuki, Yamaha, Kaw). Make sure that the oil holes in the center clutch hub are cleaned out GOOD whenever you change a clutch, and soak the plates before installing, don't just wipe oil on them. I almost always soaked them overnight for my customers back then, and would again today.

I still have to say, though, for the record: none of my Barnett clutches lasted like the Honda clutches. Not in the 305, 350s, 450s, 500s or 750s I owned or cared for, anyway. I can say that stock Suzuki clutches and Barnetts ran neck-and-neck for mileage, though. And, I always used Barnett springs with Barnett clutches, and ran Barnett springs in my 500's stock Honda plate setup to reduce the slip at startup. Others I know of tried reversing it, with Honda springs on Barnett plates, and that really shortened the clutch life in every instance I can remember.

My 2 cents' worth....

[HondaMan]

I've got some high-RPM, high gear (4th and 5th) clutch slippage problems on a basically stock K2 (pod air filters and thats it).  I had the clutch apart about a month ago and checked everything with a micrometer, all parts mic'ed like they were new, the fiber discs still had the marks from the surfacing machine on them (probably don't now though ) The real problem is that I'm not sure if the clutch components are Honda, Barnett, APE or what.  The oil passages in the fiber plates are straight-cut, not slashed and the steels are peened or dimpled, whatever you want to call it.  It clunks into first (roll it ahead while snicking into first makes it alot better though) its hard to shift, like its sticky, occasionally find neutral while shifting, never when you WANT to find neutral (its hard to believe how fast those little fours hit 10,000  ) BUT it only takes light pressure to get the clutch to release.  Everything is adjusted by the book, if the books are right.  I'm running dinosaur oil (Valvoline 20/50 4 stroke motorcycle)  It seems like the clutch is releasing waaaaay early in the stroke, 1/2 inch free play and pull it another 1/2 inch and its fully released.

I'm out of ideas (short of putting stiffer springs in it or spring spacers) so I thought I better ask the experts

Coyote:
Did you ever get this worked out?
The clutch action you're describing is what we used to call the "in-out box" action, after early Buick no-clutch transmissions: you stuck it in gear with a CLUNK and you were moving, no slip!

The holes in the clutch hubs on the K0-K4 CB750 were too small, sometimes poorly drilled or not all the way through, or could get clogged up with grit, especially Barnett plate grit, or "sat in the shed 3 winters, no oil change" grit. This then makes the hub starve the plates for oil, after which they burn, and quickly. Typically, the slippage repeated itself soon after the plates were replaced: most owners did not know to clean out the holes during plate changes. So, they'd install a new clutch, and it would burn right out.

The first thing to do is find my post (FAQ: Thought of Hondaman, somewhere in there) about "Hate that In-Out box of a clutch?" and do those clutch hub mods to your K2. It might be too late for the existing plates, but surely don't put new plates in while the problem exists, or it will be expensive!

Then, get new clutch plates. While it's apart, check the steel ones for burned appearance in spots around their faces (those are bad, for sure) and lay them against some flat plate glass and try to slide feeler gauges under the plate around the edges, looking for raised warped spots. The warpage must be less than .007" or else they will drag, causing false neutrals, missed or jump-out shift (especially in 2-3 gears) and hard-to-find neutral at very low speeds.

[coyotecowboy]

I still havent gotten around to buying a set of Barnett springs, but I checked the steels and plates on a surface table when I had it apart and they were dead flat, looked just like new.  The only time I get "actual" clutch slippage is if I'm really getting on it, and only at high speeds and in the upper RPM range, which sounds to me like the springs are too weak or just plain tired.

The Honda fiche shows a spring seat (looks like a washer) but nobody seems to know anything about them.  That would raise the spring tension, I wonder if it was a factory-approved fix for slippy clutches that came back to the dealer?

Oh yeah, I did the clutch hub mod and that did wonders for how it releases from a stop.  I also went back to the stock airbox and that made the throttle even easier to modulate off idle.  Low velocity air intake pressure difference?  Who knows?

[dusterdude]

there is a guy on ebay selling hi-po clutch springs,not sure of the manufacturer i bought a set last year but havent installed them yet.

[HondaMan]

I still havent gotten around to buying a set of Barnett springs, but I checked the steels and plates on a surface table when I had it apart and they were dead flat, looked just like new.  The only time I get "actual" clutch slippage is if I'm really getting on it, and only at high speeds and in the upper RPM range, which sounds to me like the springs are too weak or just plain tired.

The Honda fiche shows a spring seat (looks like a washer) but nobody seems to know anything about them.  That would raise the spring tension, I wonder if it was a factory-approved fix for slippy clutches that came back to the dealer?

Oh yeah, I did the clutch hub mod and that did wonders for how it releases from a stop.  I also went back to the stock airbox and that made the throttle even easier to modulate off idle.  Low velocity air intake pressure difference?  Who knows?

The stock airbox has velocity stacks inside, which very much improves the low-to-midrange mixing ability in the carbs. It also improves the full-throttle flow, so long as the air filter is new or a K&N type.
There should be a washer at the top of the clutch springs: it would likely be impossible to assemble well without one! One thing I do remember: some guys in the early 1970s I knew used some STP in their Hondas (one was a 750, one a 450, similar clutches), and both ended up with slipping clutches until we took the plates out and soaked them in solvent (I think it was naptha, but might have been trichlorothane, as it was not illegal in those days). They soaked for 2 days before the grease slicks stopped appearing. Then I soaked them in oil again, because the corks were looking rough. They stopped slipping and they were still using them when I left for Colorado 2 years later.

[coyotecowboy]

The STP raises some interesting questions.......Just after I purchased the bike, I did a full service on it and for oil I used (drumroll please)..............MOBIL 1!!!!  OOPS   I only had it in for 100 miles or so, then dropped that oil out when I pulled the clutch and did the hub mod, then switched to Valvoline 20/50 motorcycle oil.  I washed up all of the clutch parts in the solvent tank just after we had recycled it the night before, so the solvent was absolutely clean.  Then I hosed the friction discs down with ether and dried them off before I mic'ed the parts.  Do you think that in 100 miles the clutch could have absorbed enough of the friction modifiers in the Mobil 1 to be causing me problems nearly 2000 miles later? 

Any help would be greatly appreciated