I have installed Wirth progressive fork springs as I heard it is one of the best for gs500. The manufacturer sells it with a 4cm long spacer. It was horrible to compress the spring together the spacer and put back the cap of the fork tube. The spring is very strong. I put 15W oil into the fork as other rides advised it. I went for a ride alone and together with my girlfriend and I felt it very bumpy. The cornering, the braking is much better and the fork does not bottom out but is not so comfortable. I have installed a Katana 600 rear shock as well and it is much better than the stock.

I am thinking about the best solution would be to eliminate the spacer. The rider here mentioned the same solution: http://www.bikepower.net/gs500e-power/modifications/suspension-related/fork/forkpage3.htm.

What do you think? I am afraid of after this modification the sag would be too long.

People have gone to the hardware store and gotten some plastic tube and made their own spacers whatever they like. If you think completely removing the spacers would be too much, you could try making some that are only half the length and give those a shot.

When you change a bunch of variables at once, it can be hard to keep straight which one causes a particular effect. If you swapped springs, oil weight, and rear shock all at once, good luck sorting out which does what.

That said, 4cm sounds long on the spacer - mine came with a hunk of tubing to be cut down into spacers, and most of it was left over. As best I recall, about 2cm, not 4 cm for the spacers. I can't seem to find the specific directions for the GS500 set on line, just the generic instructions which don't have specific spacer lengths or each bike/spring listed, and my box & instructions are a few miles away. You can simply cut them down 1/2 cm at a time until you get to a point that works.

Fork oil level and weight also matter  - while lots of folk here seem to like very heavy oils, I'm just fine with progressives and 10W oil, and I'm not a lightweight. Oil level should be set with the forks compressed and the springs not in place. 140mm from the top, as I recall.

tt_four, DoD#i thank you for the advices.

On the official site I found the fork oil level should be 160mm at this spring: http://www.wirth-federn.de/products/de/Gabelfedern/Suzuki/Suzuki-GS-500-F-04-.html
I hope they are right

So I am planning to change the oil to 10W and use half length spacer. I hope I will find the right setup soon. As I wrote the cornering and braking have already been much better than with the stock spring.