Kawasaki Concours Forum

The C10, aka Kawasaki Concours - The Original => The Bike - C10 => Topic started by: antarala on August 10, 2019, 05:07:36 am

Title: Fork Spring Help
Post by: antarala on August 10, 2019, 05:07:36 am
Perhaps some of you old timers can help me. Two weeks ago I purchased a 2000 C10 w/34k. Nice plastics and tank (in and out). I had run into the owner at a biker thing in about 2005 and we had an interesting conversation, at least for me because I remembered him. He was a fanatic about his C10, worked at the local Yamaha dealer and his parents had owned a Honda dealer in town in the 60’s.

He has passed to wherever or whatever now and I don’t know what he did to the front springs in the forks or why and I can’t find anything in my searches.
There are three parts, a bottom spring which is approximately 1 9/16” long, a spacer made from electrical conduit 1.125 outside diameter 7 ¼” long, and at top a spring which measures 13 ¼“. Total combined length approximately 22” long. The springs have not been cut an amateur and are the same at both ends. One thing I did notice is once I backed the adjusters off the caps came off quite easily, I mean most of the fork caps I have pulled on other bikes can be a deadly projectile, you get the idea.

Title: Re: Fork Spring Help
Post by: connie_rider on August 10, 2019, 09:20:15 am
My initially thought is the short spring is the topper spring that goes into the lower portion of the forks.
           But your explanations seem to point the other way..
   Do you have the forks completely apart, and can you post a photo of the parts?
   If you quickly pull upward on the fork tube, does it seem to hit a spring as it tops out???
       {If no spring topping feel, he assembled the forks wrong and the topper spring is in the incorrect place...}
   I think this the most likely....

Another thought; PVC conduit is used when you shorten a spring to make the front end stiffer.
So,, he might have cut the spring to make it stiffer and cut it too much. {Result could be too stiff or spring bind}.
If so, he may have added the short section to soften it back, and make up for what he removed.
Do the 2 springs appear to have different wind's?

I used Progressive Brand Springs and cut 5 1/2" on my C-10.
There was concern with them having spring bind. But it worked out well.

If your happy with the front end stiffness, and "know" the topper installed correctly, just put it back together.
If not; I would take the forks apart to inspect, and then, replace the springs/spacers.

Ride safe, Ted
Title: Re: Fork Spring Help
Post by: antarala on August 10, 2019, 01:59:54 pm
Thanks for your response. Here is a pic of the one of the forks the way they came apart. I only put about 200 miles on this thing and there is so much wrong in the front end, wheel bearings, pads/brake rotors (the brake pulsation may be due to the loose right wheel bearing, but they were below minimum anyway), steering head bearings were overtightened and purple (fun to get apart). Plus a nice cupped Dunlop.

I took it up over 100 mph twice, which was damn foolish on my part, but what the hell, I'm old and that's a good way to go.

I went ahead and ordered a nice set of used forks on E-bay. It also looks like someone took a whizzer to parts of the lowers for some reason and filled part of it in with JB weld or something and painted them.
Title: Re: Fork Spring Help
Post by: connie_rider on August 10, 2019, 03:26:23 pm
Good idea.
From memory, and my memory sux..

The topper spring is now in place.
   Was it there when you took them apart?
   Is that the small spring you showed in your first post?
The tubing is steel.
  Most use PVC tubing.
The big spring goes in first, with washer** and tubing spacer on top of it, then last washer and top cap..
  You have spring/spacer in reverse order.
There is a washer under the topper spring. I don't recall one being installed there.
   I think that washer** belongs between the big spring and the tubing spacer.

Others correct me if I erred?

Ride safe, Ted
Title: Re: Fork Spring Help
Post by: antarala on August 10, 2019, 06:43:27 pm

Thanks for the help. Quite frankly, I really don't know how a C10 is supposed to ride. There are not very many around here, Harley country. I owned a 98 VFR which is as close as I can compare. The C10 didn't seem to wallow around corners as much as the VFR, but the VFR has much more power and quickness where the C10's power seems more linear. The VFR is lighter. I like the riding position much better on the C10 than the VFR even after spending hundreds trying to 'fix' it. Both to me seem to be somewhere between a heavy tourer and sport bike.

Yes, that is the way the fork came apart. My idea now is to put a stock front end on and go from there. Then I'll give it a good stop from triple digits and see how much this bad boy dives and then hit the corners hard. Though it isn't a 400lb. bike and never will be.  A 7 1/4" spacer seems a bit much to me and I don't get it. I thought maybe it was some deep secret of the C10 society.

Next up is to replace the rotted out header pipe, that crossover has been very nicely wrapped, but still leaks and gets bad behind all that plastic. Then hopefully on to regular maintenance items, driveshaft, valves, petcock, lines, sync carbs(the tank is clean and it runs well, so I don't think there will be much to that) ect., ect.

Thanks again.


Title: Re: Fork Spring Help
Post by: gPink on August 10, 2019, 07:24:54 pm
The first picture looks like a nice toy box. Would that be a hack behind the c10? Ural maybe?
Title: Re: Fork Spring Help
Post by: Rick Hall on August 11, 2019, 12:24:19 am
Stock fork springs are progressively wound, tighter (closer spacing) at one end, looser at the other end.
Progressive brand fork springs are uniform pitch, and shorter than OEM springs. A spacer is required, and provided.
Why/how you have a spring, spacer, then shorter spring is beyond me. But I will have to assume the previous owner installed some sort of aftermarket (Progressive?) fork spring.

The damper tube appears to be stock, so I can rule out Race-Tech Cartridge Emulators.

As to removing the fork cap, I hear ya! On the Concours, it's 3/4" of compression, max.

Edit to add: your springs are in all probability a Progressive (or equal) upgrade. The shorter spring fits over the damper tube to eliminate shock when the fork is fully extended. The metal spacer generally goes on top of the main spring, to prevent the spacer from rubbing the fork tube during fork movement.

In a nutshell, you're fine :)

Title: Re: Fork Spring Help
Post by: antarala on August 11, 2019, 04:30:51 am
The first picture looks like a nice toy box. Would that be a hack behind the c10? Ural maybe?
Yes, that is a Ural Retro. Regrettably, it shares some of the same bad habits as the C10, hydro lock. It has the same CVK32 Keihin carbs/vacuum operated pet cock, with a slightly different external configuration. If it hydro locks it will twist the crankshaft (it is pressed together) and that is an expensive fix. Fortunately, it has a kicker and I always kick it through at least one revolution before I hit the electric one.
It is really a hoot to ride, but requires a whole new set of riding skills.

Thank-you Rick for the info.
Title: Re: Fork Spring Help
Post by: gPink on August 11, 2019, 05:41:40 am
Thanks...nice pic.  8)
Title: Re: Fork Spring Help
Post by: connie_rider on August 11, 2019, 11:39:28 am
As you might imagine, there are many opinions on suspension. This is mine...

On the C-10, the front springs are designed to be for smooth riding and so are weak and dive easily.
For normal riding they are fine. if you sport,  it's best to stiffen the front springs a bit.
NOTE: You don't need high speed run to test.
           You can just bounce the front end while setting still and you will almost bottom the front suspension.

Some change out the entire front end or have a Suspension shop rework everything. {approx. MANY $$}

  1 fix is to buy aftermarket stiffer springs. {approx. $100)
  Another fix is shortening the OEM's and adding a spacer. {approx. $2 for PVC spacer}
        {I think this was done to your bike}

Another concern is damping control and adjustability.
  1 fix is changing oil weight and level. {about $20}
  Another fix is Race Tech Emulator. {approx. $150}
  Another is a copy of the Race Tech Emulator {appears to be an exact copy}. {approx. $35}

Question; You did not answer if the short spring from your first photo's is now on the damper tube {topping spring} and is the only short spring you have?

At this stage, I suggest flushing and replacing the oil in your new forks and install on the bike.
Then ride it for awhile and determine if you want to modify the ride.
If you do, we can assist.

Ride safe, Ted
Title: Re: Fork Spring Help
Post by: antarala on August 11, 2019, 05:48:59 pm
Yes Ted, that is the only small spring I have. The reason I placed it with the other spring and spacer is because I thought it might be part of the 'spring service limit', it is written in the Gospel of ZG1000 so it must be true, the minimum limit is 20.98". With the main spring and spacer it is only 20.75", below specs, though with that long spacer in there that may change things. The new limit it is 21.47" and that fell in with adding the topper. That is the reason I put the tape measure beside it, to show the length.

I will go with your suggestions, once I receive the new/used fork. I have a couple of quarts of 15wt. fork oil, which I use in everything, so that will be 1st. I'll ride it a few days and hopefully do not become asphyxiated by the leaking exhaust and run off a cliff in the mountains. I don't have many brain cells left which I can afford to lose, so I'll try to stay away from stop and go traffic, which is easy to do in Green Acres.

I'll keep you posted.


Title: Re: Fork Spring Help
Post by: antarala on August 12, 2019, 12:30:10 pm
Well, I am back again to question the brain trust. The bad news is the seals I received with the front wheel bearings are wrong, so I went ahead and ordered a new tire (that will teach them). The good news is I got the forks and they are very nice and straight, with no apparent mods and they came with a triple tree which I may need since I had to beat the other out of the frame with a mallet.

Three questions.
1. Looking at the picture are those stock springs?
2. They measure 20-3/4" the same as the old setup which is under specs. Is it possible the book is wrong? Say it ain't so.
3. Do you think it would hurt to use the old washers under the springs?

Thanks again.

Title: Re: Fork Spring Help
Post by: connie_rider on August 13, 2019, 07:56:27 am
Need to go check my old post, but I think mine were also 20 3/4" before I cut them.
Don't worry about it. You should be more concerned with front end dive than the length of the spring.
Length can be made up with spacers or preload...

Washers are no problem.

In your image, note that the new springs are wound differently.
1) The tightly wound section is not on your originals.
      If they had a tightly wound section it was probably cut off to stiffen the spring.
         That is what I did on mine...
2) More importantly, the wider winds on the new set up, are more closely wound than your originals.
       NOTE: Wire diameter and material also effect stiffness, but this tighter winding suggests the new springs are a softer
                         spring and will dive more.

I still say, put it together and try it.
You might like the ride... Many like it soft...

Once assembled, bounce the front end.
I suspect you will be able to use almost all of your suspension travel by just bouncing the front end.
If yes, and if you want to stiffen it, more discussion will be needed.

Ride safe, Ted
Title: Re: Fork Spring Help
Post by: antarala on August 13, 2019, 04:33:36 pm
I couldn’t wait for the tire and seals, so I popped the old seals back in for now, they’ll be changed with the tire.

Now what I did.

I put the washers from the original forks under the new/old springs and set both adjusters at the third line from the top (3 lines showing).
I went on a two-hour road test. There are some treacherous roads in these parts (not to mention the wildlife), so I tried to stay on these roads most of the time. The front Dunlop gets squirrelly over 80, so all testing was done under that speed.

After burnishing the new pads/rotors in I did hard braking @60mph, hard enough so that the brakes locked. To be honest, yes, the front end dipped a little, but it was nothing that bothered me or I felt like I was losing control. I have ridden much worse. I can live with it.

The rear shock needs some adjustment help and I am sure a fluid change. It doesn’t dampen well over certain bumps (just before it goes airborne). Like a pogo stick. When I got the bike, I checked it and it was set at 5 psi and at #4. I set it at 18 psi and #2 thinking that was stiffer ride. I have been studying the factory manual and it says #2 is for a 150lb. rider. Well, I haven’t seen that in 50 years. So tomorrow after I recheck the steering head bearing adjustment that will be the sortie. Play with rear shock.

The fork adventure is over and I have been forked by a C10. Next up will be the exhaust header, we’ll see if we can break a stud or two. That is always fun.
By the way, I love the bike, it is a keeper. I like the seating position, the engine braking, the way the bike doesn’t ‘push’ you to go faster (it is as content at 40 as it is at 80) and it doesn’t do a 100 in 1st. It is what it is, a 700lb. sport bike painted in Arrest Me Red.
Thanks, Ted and Rick, for your support and advice.
Title: Re: Fork Spring Help
Post by: connie_rider on August 13, 2019, 07:45:54 pm
Ok. Best of luck.

Ride safe, Ted
Title: Re: Fork Spring Help
Post by: Rick Hall on August 13, 2019, 11:09:03 pm
Long springs are OEM. Short springs, with spacer, are Progressive (or equal) upgrade.

As Ted mentioned, the OEM springs have quite a bit of travel, they may appear mushy with aggressive driving. Cure is to shorten them up and add a spacer, or go with different springs. Changing to 20w oil helps too.

Fork oil nice, regular straight weight auto oil works too but have to change it more often. Fork, and shock, oil takes a beating.

Title: Re: Fork Spring Help
Post by: connie_rider on August 14, 2019, 06:17:39 am
I have a set of springs here that appear to match the windings of your shorter springs.
Mine have tightly wound coils at the top and I think they are Progressive Brand.
I took them out of my bike when I installed the springs that are in it now.
These are 21 2/1" long.

I'm sure your tired of springs right now, but I suggest you install the short springs and spacers when you get a chance.
    {to feel the difference}
The change be done with the forks on the bike and would be EZ to do quickly when changing your front tire.
 I think they will give you a firmer ride.

Here is a video on setting spring sag. There are many video's available on You tube.
Ideally you want about 35-40 mm of sag {with you on the bike}
With the springs you have now, I suspect you have about 50-60 mm sag.
https://www.youtube.com/watch?v=ZtzTyCKh5fY (https://www.youtube.com/watch?v=ZtzTyCKh5fY)

On the rear, I used about 40 psi and #2 or #3 setting.
I now have a C-14 shock on the rear of my C-10.

Ride safe, Ted