CB750 Nighthawk clutch replacement

I am trying to replace the clutch on my 1992 CB750 Nighthawk. I ran
into a problem trying to get that big nut off the end of the tranny
shaft. I drilled out the indented part of the nut and still could not
get it off. Is there an easy way to get this off? Also, is it reverse
threaded?
Thanks for the help.
Dan

 

Why are you trying to remove the clutch basket anyway, unless it's
damaged? A new clutch is just plates and springs, and no need to remove
the basket at all.

Looking closely at the nut will tell you if it has a left-hand thread,
unless you've buggered it so badly the threads can't be seen.

I have a horrible feeling you've done something very, very stupid.

 

No, it's not reverse threaded, but it is installed with a torque
wrench, probably about 100 foot pounds of torque. The big nut holds the
clutch inner hub onto the transmission mainshaft. If you just want to
replace the friction plates, this nut doesn't have to be removed at
all. If you need to replace the needle bearings or bushing or the
clutch basket or the inner hub itself, that big nut does have to come
off.

If you really really really need to remove the clutch inner hub you'll
need a long lever arm, like a 2 foot long cheater bar on your ratchet.
And you'll have to have the transmission in gear and stop the rear
wheel from turning. I usually stick a stout piece of wood between the
spokes of a cast aluminum wheel so the wood rests against the swing
arm.

DO NOT, under any circumstances, try to prevent the clutch basket from
turning by wedging a screwdriver or any kind of lever between those
projecting aluminum knobs that guide the clutch springs!

You'll just break one off and come back here admitting that you've
really screwed up.

You need an owner's manual to tell you what exact torque is required on
that big nut.

Assuming that you really really really need to remove it at all.

 

Fair enough. How unusual. What a bloody silly design.

 

[snip]

Please just go out and buy a breaker bar instead. The chance of injury
as a result of your ratchet slipping is low (unless you've got one of
Craftsman's newer ratchets, those things slip _all_ the time), but $25
gets you a solid steel bar: no slipping and it will take more force
(e.g. longer cheater bar) before breaking than a ratchet will.

--
Later,
John



'indiana' is a 'nolnn' and 'hoosier' is a 'solkk'. Indiana doesn't solkk.

 

What a crazy idea! Honda invents the inside-out clutch, with the
pressure plate behind the center hub! What were they thinking of? (1)

Every motorcycle clutch that I've ever worked on had the pressure plate
outside of the basket, right where you could get at it and easily
replace the clutch pack, regardless of whether the throwout mechanism
was a through rod, ball and ramp, gear and sector or whatever.

Maybe Honda just doesn't *want* riders to be able to repack their
clutches easily?

(1) For their next technological tour de force, Honda will invent the
inside-out peanut butter and jelly sandwich, applying the sticky stuff
to the outside of the sandwich and pressing the dry sides of the bread
slices together, and whatever the sandwich eater has to do to keep the
goo off his hands is his own problem.

 

It really looked to me like I had to take off the inner hub (not the
basket) to get the friction plates out.
-- I really don't like this design.
Is there some special tool that i can get at Home Depot that will fit
that, or am I stuck making something?

Dan

 

Yes, you will have to remove the center hub, because you can't get the
friction plates past that flange on the outside of the center hub. In a
conventional design, you would remove the four bolts holding the
pressure plate on, the springs and pressure plate would come out and
you could slide the friction plates and steel plates right out of there
without removing the center hub.

For whatever unknown reasons, Honda was reversed the normal assembly
and put the center hub and pressure plate in there backwards, at least
according to Mark's drawing:

http://www.visi.com/~olsonm/1992_cb750_clutch.jpg

I agree. I don't see anything rational at all about assembling a clutch
backwards from everybody else's clutch.

Is that #18 nut a hex nut, or is it some weird special Honda nut that a
hex socket won't fit?

If it's a special Honda nut, you'll probably need to buy a special tool
from Honda
or go to www.denniskirk.com and check out the special clutch spanner
P/N 281970
or 28-1970 (page 674 in the paper catalogue)

The description says it fits Honda CB, CL, CT, SL, XL twins and singles
90cc to 500cc.

Does that tool look like it will fit your clutch hub nut?

 

Another question: the paper gasket came off in a couple of pieces. Can
I get away with just using RTV, or should I get the replacement gasket?
Dan

 

http://www.visi.com/~olsonm/1992_cb750_clutch.jpg

no doubt, I changed my 82 xj750 yamaha in 45 minutes, and spent 30 of that
looking for tools...

 

my 82 xj750 was same side, actualy the actuator was on the cover, and I
just toook off the 5 or 6 screws for the springs, and swaped out the stack
of discs, and reversed the dissasembly...

 

Well guys, the clutch is on. I made a tool by taking an angle grinder
to a socket until there were only four points left. Worked well enough,
but doesnt last long because the heat ruins the hardness. RTV'd the
hell out of it, and there it is.
I used EBC friction plates and the 10% stiffer springs. The clutch
definitely doesn't slip anymore, and I found myselft a couple inches
farther back on the seat a couple of times.
One issue though: when I start release the clutch, and slip it a little
at low RPM, it pulsates rather harshly. Its not the engine. The engine
runs fine. The clutch just feels really grabby. Is this normal, or will
it go away when the plates wear in?
Dan

 

That sounds like clutch shudder or "judder" as the Brits would say.

Did you soak the new friction plates in oil overnight?

Are all of the springs the same length?

Have the springs worn grooves onto those four guides sticking out of
the pressure plate?

Are all four bolts tightened the same amount?

Are any of the steel plates warped?

 

I soaked the plates for a couple of days. I installed new springs, but
did not check the length. I did not notice any damage or unusual wear
to any components. The torques should be reasonably close, but I didn't
use a torque wrench. I really wonder if the steels were warped, but I
doubt this would be the problem because it did not do this before.
Dan

 

You can get into trouble with a torque wrench, trying to tighten oily
steel bolts.

A beam-type torque wrench may never indicate the specified torque, a
clicker may never click, as friction on the threads don't reach the
level that indicates there is enough
*tension* on the bolt to keep it from loosening.

I only had to break one steel bolt in an aluminum head before I
relaized what was up.

Now I use brake fluid or aerosol carb cleaner to degrease bolts and the
holes they thread into.

You can check steel clutch plates by laying them on a piece of glass
and seeing if they touch the glass all the way around.

 

Thanks for the tips. I like the glass idea. Is there any chance that
this shudder will just go away as the friction plates wear in?

 

I suppose the shudder might go away. One would hope so to avoid
dissassembly and inspection.

The springs on the pressure plate of a car's clutch are sometimes
adjustable so the
single pressure plate touches the single friction plate all the way
across it at the same time. Some British motorbikes have been made with
adjustable springs on the pressure plate, but Japanese motorcycles
usually just have the mechanic tighten the pressure plate bolts all the
way and rely on a separate spacer, or cast-in spacers like the ones on
your pressure plate. It is possible that you didn't get a bolt all the
way tight but thought you did. This might be because of (oh crap!)
cross threading the bolt.