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General Category >> Rubber Side Down! >> Cheaper front suspension upgrade?
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Message started by kojones on 03/28/18 at 09:14:36

Title: Cheaper front suspension upgrade?
Post by kojones on 03/28/18 at 09:14:36

A few months ago I found out of new cartridge emulators, manufactured by Korean YSS.

http://www.yssusa.com/products_yss_pdforkvalve.html

As the Racetech emulators are quite expensive when shipped to Europe I decided to get a pair of these (72€ incl. shipping), size 310, suitable for Suzuki GS500 and others with same sized fork tubes.

Using the spring calculator at Racetech site I found out that they recommend same springs for Kawasaki Ninja 250 as they do for Savage, and they also told that the stock springs for the Ninja are 0.65 kg/mm. So, these springs should fit the mighty Savage as well ;)

As they're not that expensive ($22) I decided to order a pair: https://www.partzilla.com/product/kawasaki/44026-0126

I got the inspiration to do this from Gary_in_NJ's excellent thread: http://suzukisavage.com/cgi-bin/YaBB.pl?num=1498156004/1

Title: Re: Cheaper front suspension upgrade?
Post by kojones on 03/28/18 at 09:17:23

Disassembly of the front forks was easy, here is the stock progressive spring vs. the new Kawi spring, which are 15mm longer and have slightly stiffer feel.

Title: Re: Cheaper front suspension upgrade?
Post by kojones on 03/28/18 at 09:18:51

YSS instruction manual https://www.yss.co.th/downloads/20161222023100.pdf states that this size of fork tubes requires six 8 mm holes. So, let's drill.

Title: Re: Cheaper front suspension upgrade?
Post by kojones on 03/28/18 at 09:22:22

YSS manual stated that the preload spacers should be shortened 14-17mm. The new springs were slightly longer, so I decided to cut 30mm out of the stock spacers. So, 14mm of preload.

Title: Re: Cheaper front suspension upgrade?
Post by kojones on 03/28/18 at 09:28:47

Poured some 15W oil in, measured it so that the oil level is 75mm from top of the fork tube, according to Clymers. YSS manual said to add 2 turns of preload to the fork valve springs, so I did just that.

Upgrade wasn't that hard, took a couple of hours and a few beers with a friend.

The front end feels much better already, much faster response and smoother feel. Have to wait a few weeks before I can take it to a test ride ::)

Title: Re: Cheaper front suspension upgrade?
Post by justin_o_guy2 on 03/28/18 at 10:04:08

Did you do a
Panic Stop Dive test
Before and after?
Results?
How happy are you with the performance?
What do you weigh?

Title: Re: Cheaper front suspension upgrade?
Post by kojones on 03/28/18 at 10:24:45

3D2224233E3908380830222E65570 wrote:

Did you do a
Panic Stop Dive test
Before and after?
Results?
How happy are you with the performance?
What do you weigh?

Too much ice and snow on the roads to do proper testing just yet ;D
That spring rate should be a decent match for a lightened Savage and a 80 kg rider.

Title: Re: Cheaper front suspension upgrade?
Post by Gary_in_NJ on 03/28/18 at 10:27:38

Great report. I think a 75mm air gap is too much oil. I started with 120mm and settled on 130mm. With that much oil the last 1/3 of fork travel will be very stiff, if you can access it at all.

Title: Re: Cheaper front suspension upgrade?
Post by kojones on 03/28/18 at 10:32:45

5C565258535A5E57090F0B3B0 wrote:

Great report. I think a 75mm air gap is too much oil. I started with 120mm and settled on 130mm. With that much oil the last 1/3 of fork travel will be very stiff, if you can access it at all.

Good info. Luckily it should be easy to remove the excess oil with a syringe and some rubber tubing, just have to calculate the volume.

Title: Re: Cheaper front suspension upgrade?
Post by Gary_in_NJ on 03/28/18 at 13:57:28

Check my suspension thread or my build thread, I’ve done the calculations

Title: Re: Cheaper front suspension upgrade?
Post by Gary_in_NJ on 03/29/18 at 12:29:03

Here is the figures you'll need to adjust the oil height:

For the forks used on the CS-1 Café, each 8.55ml (0.289oz) of oil added or removed equates to a 10mm change in oil height (the forks have an ID of 33mm and solving for this equation gives us the volume of fluid: Volume = Pi x R^2 x Length).

I checked my records and my air gap is actually 140mm. So if the goal air gap is 140mm and you're at 75mm, that's a difference of 65mm. Each 10mm equals 8.55ml so 6.5x8.55 = 55.58ml to be removed.

Title: Re: Cheaper front suspension upgrade?
Post by Matchless G11 on 04/04/18 at 14:47:14

What is the ft fender you are using?
I am looking for a different one for my project.

Title: Re: Cheaper front suspension upgrade?
Post by kojones on 04/04/18 at 22:02:01

253C3232646427302130363E666160550 wrote:

What is the ft fender you are using?
I am looking for a different one for my project.

It's a stainless fender bought from ebay, some greek seller. Still need to make a mounting bracket for it from stainless 115mm tube.

Title: Re: Cheaper front suspension upgrade?
Post by kojones on 04/12/18 at 13:28:00

Still waiting for a syringe to get rid of some oil, but I did measure a bit.

From rear shock top mounting nut to ground: Free sag 10mm, loaded sag 30mm.

Front fork tube compresses 10mm by the bikes weight and with me on the saddle another 30mm..

These seem to be quite ok?

If I just could take it to a test ride, it’s almost +10 degrees outside. Still have to wait a few weeks for a new longer chain and larger sprockets :'(

Title: Re: Cheaper front suspension upgrade?
Post by Gary_in_NJ on 04/12/18 at 15:49:18

I like those sag values. Spot on.

Title: Re: Cheaper front suspension upgrade?
Post by kojones on 06/11/18 at 23:30:58

I still haven’t found a pothole that would bottom out the suspension, the forks feel excellent. The roads in Finland are in quite bad condition this year, but I feel very confident on the twisties. My friends don’t ;D

On loose gravel the front feels a bit light, I think that dropping the forks two inches would help with this, more weight to the front. But I don’t want to change to clip-ons or reduce the travel, so I think I’ll just have to get used to it.

Title: Re: Cheaper front suspension upgrade?
Post by kojones on 07/01/18 at 13:36:25

I realised that the springs can be cut to achieve a higher spring rate. When these Kawasaki springs are cut to Racetech spring length of 377 mm their rate will be 0,73 kg/mm. And with the Savages limited travel they can be cut even more.

Sold my Savage and bought an airhead BMW, going to use these same springs and fork valves in it.

Title: Re: Cheaper front suspension upgrade?
Post by ohiomoto on 07/02/18 at 05:58:50

6F6B6E6B6A6177040 wrote:

-------------------------------------------------

Sorry to hear you sold the Savage have fun with the BMW.

As for lowering forks without reducing travel... There other ways to do that...

[media]http://www.youtube.com/watch?v=HNiblp32Qq0&t=109s[/media]