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Progressive suspension spring upgrade and fork oil cheat

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chris900f:
Decided to install the progressive springs today with 1010km on the clock. These springs are the replacement set for about 20 bikes listed, including the Ninja 500...and also some bigger bikes.



I'm going to cheat and just swap the springs and "most" of the oil.



I use a 6x1mm threaded rod as a dipstick. The threads hold the oil. making it easy to mark the spot. Measure the distance (50cm). So that's the oil-level, with the springs in and the bike on
the centerstand, with the front wheel jacked up just a hair so there is no weight on the front wheel.




The stock preload is pretty high.


After fishing out the springs and spacers with a magnet, it's time to get rid of the old oil.

I found these x-large medical syringes at an industrial plastics (resin molding) shop, where they are used for fine measurement of resin hardener. $5.00 a pop.

I'm using very flexible 1/4" fuel line...it's a little messy.



After you get the top half empty, you need to insert the rod into the hose to get it down to the bottom of the fork. Remove the rod and then use the syringe.



After getting out as much as I could, the threaded rod still measured a couple of inches of oil. I probably removed about 80%

I put in the new springs and used the syringe and dipstick to get the oil to same level as my original measurement. Note how high the springs are
in the tubes. Recommended preload is .75" or about 20mm. I'm using Bel-Ray 15w because I had it left over from my 900.



The instructions say that it doesn't matter if you have the closer coils at the top or bottom of the fork. I decided to run them with the more open coils
at the bottom. If the closer coils were down at the bottom they would take up more space, and therefore I would get less oil at the same height on the dipstick;
so for the sake of a little more dampening I'll run them with the close coils at the top.

I also installed these "bar-backs" They fit with no problem, I cut one redundant cable tie and the cables/hoses are all free with no strain. The NOS set I got cheap on ebay needed a little work with a tap to open up one of the holes but it only took a minute to fix it.



The bar-backs have the added feature of allowing you to access the springs and spacers without removing the bars. Not quite as good as adjustable preload caps but not bad.



I started with just under the recommended .75" about 15mm, a bit too soft so i moved up to a 20mm, then a  25mm(1 inch) spacer and finally settled on 34mm. This was about as
much as I was willing to use as it gets difficult to get the forks caps in safely.

These springs are quite firm under hard stopping and pretty much eliminate dive, but still have near-stock sag and ride height. They are not particularly heavy/stiff so heavier riders may not like them. I find that they can handle the rougher "b" roads, including bumps that would bottom the stock springs, very smoothly and the rising spring rate works well at speed and in the corners.

I installed the R6 shock a few weeks ago, and coupled with these springs the improvement is night and day.  Suspension mods are probably your best bang-for-the-buck on the GS500s. The bike just works and feels better under all conditions.












SK Racing:
Thanks for the nice how-to. :cheers:

I will probably do mine as well sometime in the future now that I have the R6 rear shock installed. 

chris900f:
Thanks, what do you think of the R6 shock? Were you able to get a soft enough ride?

Are you going with the Racetech or the Progressive fork springs? I probably would have gone with the Racetech's because they are so popular here,
but the import cost/exchange and shipping costs had me looking at other options.

SK Racing:
The R6 rear shock is superb. Preload is on position 2 as per your recommendation and I managed to dial in a much smoother ride by playing with the slow and fast compression settings. Last Sunday on the Gentleman's Ride I did about 80km and my back was fine afterwards. With the stock shock the previous week, I suffered from back pain after a 10km ride.

I'll probably go for the Sonic springs if and when I upgrade the front. It will have to be a special import as we don't have access to such luxury upgrades off-the-shelf where I live.

chris900f:
Cool. I'm glad to hear the shock is working out for you. I noticed that with the R6 shock set-up
the forks don't dive nearly as much, even with the stock springs.

What did you do with the compression settings?...I still haven't changed mine from the Yamaha stock set-up.

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