any special steps required to change the fork oil in a '91? Mine has the drain holes at the bottom of each forkleg.

I've explored this in the past but the bolts at top of the forks seem unusually tight.

Any info is appreciated.

Greetings from Ottawa. Things that might help with the caps:

loosening the top triple clamp pinch bolts
6 point socket
long pipe on the ratchet handle

"loosening the top triple clamp pinch bolts" definitely do this!  Make sure your front wheel is also off the ground to relieve pressure from the springs on the caps.

Also, if possible, go take a decent ride before you do it to re-suspend all the particles before you drain the fluid.  We also made a little hollow screw with a 12" rubber hose attached to thread into the drain screw when draining so I can direct the fluid into a container.  I put a dab of Yamabond on the drain screw before I put it back in to make sure it seals well.

to refill, I've even measured the drained fluid (in a beaker) and pulled a vacuum on the air cap Schrader to suck the exact amount of fork fluid back in thru the little hose.

RF87 - interesting method.  i have been procrastinating fork fluid change on my 87 cause of the gen mar risers but now I am excited.   do you feel most of the fluid was changed according to the capacity each leg is supposed to hold?

...do you feel most of the fluid was changed according to the capacity each leg is supposed to hold?

There's really no where for it to pool that I know of because pretty much everything comes out.  I let each leg drain for about 10 minutes then suck the new fluid in and put the drain screw back in.  I do this in the middle of the season and the end of the season - fork fluid is cheap for the volume you use.  Each leg gets about 13 ounces.  Every 5-6 years one of the seals starts weeping (probably somewhat normal) so at the next tire change I tear it all down to get any gunk out and replace the seals.

A more accurate way to put in fork fluid is by fluid level measurement.
BUT, RFH has an interesting idea. Will make adding fluid pretty easy to do.

To get all the fluid out I have a suggestion;
(On my 86) I used a milk jug to drain and catch all the oil from the fork legs.
To do this, I cut a hole in the side of the milk jug and slid it up over the bottom of the leg.
I then pushed a slender screwdriver thru the opposite side and removed the screw.
Fluid would spray out.
Lastly, I put a little air pressure in the fork to push out remaining fluid.
In this way, no fluid was lost.

The only problem I see with is plan is that some of the fluid sticks to the inside of the jug, springs, and inside of the fork leg.   (That amount isn't captured for measurement).
This (and leaks thru seals etc) could lead to the measured fluid quantity being too little.
Insufficient fluid quantity will effect the working of the shock more than the fluid viscosity, so it's very important.


I know RFH, so I assume he is using his measured amount (and adjusting a little) per the specifications from Kawasaki?

To qualify the quantity, it would be interesting to use his method, and then remove fork cap/spring, etc to measure the fluid level.   
(With fork leg compressed, this should be approx. 6 1/2").
Once this is done, (and the exact quantity determined), you could always use the same quantity.

Ride safe, Ted

Ted got a C14 and he's forgetting ALL of his C10 stuff (almost).

The early models thru '93 that the OP has are checked with forks extended (wheel off the ground) and springs out.  The fluid should be 355mm (a hair less than 14 inches) from the top of the tube.  In all the track days and hard riding I've done, I've never noticed any "feel" issues with there being a few mm difference in the fluid level between the forks (which there may or may not be)

FYI, I have 5" of PVC pipe and 3/8" worth of washers replacing the soft coils (close wound) and use 15w oil.  That would be a different discussion.

The early models were thru '93 that the OP has are checked with forks extended (wheel off the ground) and springs out. The fluid should be 355mm (a hair less than 14 inches) from the top of the tube.

Ahh, Grasshopper, ya done hurt my feelings.   
Mebbe I should have been more specific;   
  After I discovered that it was difficult to accurately measure the 355 mm fluid level, I DEVELOPED an easier method.
  ie; I compressed the forks and measured the fluid level.
NOTE: In later model C-10's Kawasaki did the same thing.. 
 
 (With springs out) and forks fully compressed,, the Oil level can easily be seen and adjusted.
    Fluid level will be approx. 6 5/8" - 6 3/4"...
    I discovered that (For a better ride) it's good to set that level at 6 1/2".

Because RFH has come up with an easy way to replace the oil without removing the fork tubes, I suggest you go a step further.
  After accurately setting the level, drain, capture, and record the fluid quantity.
  Record that quantity and use it for future fork servicing.
 
PS: I know that some won't believe a "forgetful" old timer.  <grin>
           But,,,,,
      Since (using RFH's method) you will be able to change fluid whenever you wish,
        you may want to do it cheaply in a more frugal manner.
      Consider this;
         The fork oil for the C-10 is;  10-15 weight Anti Foaming Hydraulic oil.   
         Automatic transmission fluid is; 10-15 weight Anti Foaming Hydraulic oil.
      ATF works exactly the same as fork oil, is readily available, and costs less.

Ride safe, Ted

Be careful using ATF, viscosities vary widely. Bite the bullet and buy the correct tool for the job-fork oil.

Hmmm, the factory manual recommends motor oil.

Hmmm, the factory manual recommends motor oil.

I once tried 10W40 motor oil on an old CB750.... Drained that crap out right quick!

Geez, you guys are tough. 
As I sed in previous note;  PS: I know that some won't believe a "forgetful" old timer.  <grin>

Cholla, (not being critical of you, but) have you tried the tranny fluid?
If not, try it before you say it won't work.
You might be surprised...

Lots of things that members of this club have done to the Concours are not supposed to work.
But they did.

Have to admit though; Cholla's right about the viscosities varying.  (I had forgot about that).
Back when we did it, (we were poor and initially did this in our dirt bikes).
We did a simple test to determine the fluid viscosity.
  ie; We; had a Funnel with a tiny opening.
              Poured a measured amount of fork oil thru it and timed it.
              Then we repeat the test with several Tranny Fluids (and some hydraulic fluids).

Since that time, others in the club have done the same.
(Somewhere in the COGdom there is a chart of the results)

As I sed, We did several brands and found that there were differences.
 Those differences were not as extreme as you might expect.
In our case, we simply selected 1 brand that matched the fork fluid viscosity, and used only that brand.
But all worked.

In this case, we're talking with someone that has never changed his fluid, is using a in-exact quantity of fluid (sucked into the forks), not doing the more precision (measured level) , on a early Connie with, only a  small amount of travel (compared to 12" in a dirt bike).

I honestly don't think the difference will be noticeable.
But, if it is noticeable,,,, he now has an easy/quick way to change fluid for a comparison...
And it is also a cheap way to flush his forks.

Which was my point.  The tranny fluid is a cheap way to do fluid changes, and it will work.

Ride safe, Ted
 

No service manual in front of me, but anyone flush with mineral spirits?
If I recall correctly, thats procedure on other bikes.

If the flaming is about begin, let me get my kevlar/nomex suit on

I've used gasoline and/or parts washer fluid when I do a full teardown with no ill effects.  Just air dry good when done.  The internals seem to get a film on them that requires a brush and solvent to get it loose.

Never said ATF won't work, I said viscosities vary.
And, you don't want to use Type F as it is a bit gritty. Fork oil isn't expensive and you know exactly what you have.

My factory manual only specs 10W20. Typically that's fork oil.
I used 15W with Progressive springs on my 97. I wold have liked it a bit more sensitive to small bumps but it NEVER bottomed under braking again.

RF - that drain screw is pretty small.   Drilling a hole in a screw would seem to require a tiny hole.  Do you warm the oil before sucking it thru the screw?

Whoa,,, No flaming intended.
Cholla my apologies if it sounded harsh.

Many decide something won't work (and won't give something a chance) because something is standard practice.
It bugs me when they follow the herd, rather than trying new things.

Was just saying; give this a try before saying "it won't work", and/or "MUST use fork oil".
It works!!

Ride safe, Ted

PS: Mebbe I should add; ATF is also a good cleaner to use as a flush.  <evil grin>

No problems, my pointis if ya get fork oil you know if you use 15W and it's too firm, switching to 10 is the next step down. With ATF ya never know what you'll get. Right tool for the job.
Yep, the drain screw is small, remove the fork cap first to allow air in as the oil goes out.

Used ATF before, it worked, was better with 10W fork oil.

I am mainly curious how easy it is to pull oil into the forks via the screw hole...

Secondly, what type (dex III or other)?

Ok, Cholla, I see your point now.

Summit, back when we did this a lot, we used Amalie Type F Fluid.
Now, I would select a Dextron Synthetic and stay with the fluid you select.

Ride safe, Ted

PS; I too would like to know about the hole in the screw and the time required.



Ride safe, Ted