FX Susspension

Just got a few questions regarding the KYB SSS forks on the FX.

 

I'm finding the forks to be way to stiff for my weight 75kg/165lbs. The initial part of the travel is fine then they seem to go rock solid. This is with 2 clicks off fully soft.

I believe the FX comes out with 4.4N/mm spring rate and using the race tech guide its telling me I should be at 4.2N/mm.

Here is where it gets confusing. Whilst I was dialing my suspension in I had a ride of a 2014 yz250f  with stock suspension but it felt alot more plush/smooth and I could feel the forks using heaps more travel of the fork and it felt fantastic but from what I can find is that the 2014 came out with a 4.7N/mm spring rate.

 

So the question I wanted to ask was how much of a difference will fork oil level/quantity make to the harshness/stiffness of the forks?

I have read that the FX has an extra 5ml than the new WR which puts it in at 335ml with a working range of 300ml-350ml.  

Is it possible to just syringe out some fork oil to play with levels in these KYB SSS or do they require to be disassembled ?

 

Also for when I do get some new springs are these forks tricky/hard to change your self or fairly straight forward?

 

 

The oil level will affect the last 1/3 of the stroke.

You can remove the tubes from the bike, hold them upside down and syringe some oil out of the air bleeders.

 

Not only a different spring rate, the FX and WR most likely have softer 'enduro' valving versus the F

so depending on your usage, not comparable on a motocross track / large jumps.

 

Here's a video on how to service KYB SSS forks, search for part 2, it shows re-assembly.

Not explained but good practice, turn the comp/reb adjustment screws to full 'soft' before dis-assembly.

(avoids needle damage, I've unfortunately experienced it...)

 

Edited by mlatour

Just got a few questions regarding the KYB SSS forks on the FX.

 

I'm finding the forks to be way to stiff for my weight 75kg/165lbs. The initial part of the travel is fine then they seem to go rock solid. This is with 2 clicks off fully soft.

I believe the FX comes out with 4.4N/mm spring rate and using the race tech guide its telling me I should be at 4.2N/mm.

Here is where it gets confusing. Whilst I was dialing my suspension in I had a ride of a 2014 yz250f  with stock suspension but it felt alot more plush/smooth and I could feel the forks using heaps more travel of the fork and it felt fantastic but from what I can find is that the 2014 came out with a 4.7N/mm spring rate.

 

So the question I wanted to ask was how much of a difference will fork oil level/quantity make to the harshness/stiffness of the forks?

I have read that the FX has an extra 5ml than the new WR which puts it in at 335ml with a working range of 300ml-350ml.  

Is it possible to just syringe out some fork oil to play with levels in these KYB SSS or do they require to be disassembled ?

 

Also for when I do get some new springs are these forks tricky/hard to change your self or fairly straight forward?

Make sure you give them enough time to break in. Mine move a lot better after about 15-20 hours.

The first few rides felt like I could ride an SX track with them.

Thanks mlatour for the info and video!

I have only put about 9hrs on the bike in total.

 

I have just been trying to work out why my forks seem so much harder/harsher than my mates 14 yz250f. 

Like mlatour has said the FX has lighter springs and the valving should be done in a way to be more enduro friendly (softer)

Testing both of the bikes back to back was on a hard park wooped and chopped up bush enduro track.

Make sure the fork tube where it clamps around the wheel axle is in line and not causing binding.

Release any air pressure within the fork before you ride.

Make sure the fork tube where it clamps around the wheel axle is in line and not causing binding.

 

 

Here's a vid on checking the front wheel for stiction.

 

https://www.youtube.com/watch?v=siSIue3IWeI

 

I'd give them a chance to settle in. If it's still a problem, then pull some oil - small bit at a time. They shouldn't be harsher than a YZ.

BoyceyAus- Try turning your comp clickers back in 3 or 4 clicks. My experience with the SSS forks has been that they don't work very well if you back the clickers out too far. It seems like if you're within a few clicks of max out, that's too far out. The reason being, that the forks will blow freely thru the travel quickly and rather than absorbing with dampening.

 My experience with the SSS forks has been that they don't work very well if you back the clickers out too far.

 

Bazooka, is the same true for maxing them all the way in?

Gatorfan- I've never tried cranking them in all the way. I'm usually backing the clickers out for a softer woods ride over the small stuff.

They need to be revalved a bit, but generally they have a good stack but in my opinion there is too many face shims for most folks, 160 - 180lbs or so.

Does anybody have the shim stacks measured yet that they could post?

They are in the suspension section :)

 

std FX 

Forks

 

BV

32 x 0.11 (22)

29 x 0.11

32 x 0.11

30 x 0.11

29 x 0.11

28 x 0.11

27 x 0.11

26 x 0.11

24 x 0.11

22 x 0.11

20 x 0.11

18 x 0.11

16 x 0.11

14 x 0.11

12 x 0.11

10 x 0.25

20 x 1.60

11 x 0.25 (3)

 

MV

20 x 0.11 (4)

17 x 0.11 (3)

11 x 0.20 (2)

12 x 0.25

15 x 0.30

17 x 0.30

Collar = 5.25mm

Float = 0.25mm

Bleed hole = 1.2mm

 

REB

20 x 0.11 (4)

14 x 0.11

18 x 0.11

16 x 0.11

14 x 0.11

12 x 0.11

11 x 0.11

10 x 0.25

 

Springs

44mm x 471mm x 0.46kg

Preload = 7mm

 

Std Yz250f 2014 which was refered too above 

BV

32 x 0.11 (25)

30 x 0.11 (4)

28 x 0.11

26 x 0.11

24 x 0.11

22 x 0.11

20 x 0.11

18 x 0.15

16 x 0.15

15 x 0.20

20 x 1.60

12 x 0.20

14 x 0.11

18 x 0.11

20 x 0.11

22 x 0.11 (3)

 

 

MV

20 x 0.11 (4)

17 x 0.11 (2)

10 x 0.20

11 x 0.25

12 x 0.30

15 x 0.30

17 x 0.30

 

Collar = 5.30mm

Float = 0.25mm

 

 

Reb

20 x 0.11 (3)

18 x 0.11

11 x 0.11

18 x 0.11

16 x 0.11

14 x 0.11

12 x 0.11

11 x 0.30

16 x 1.60

 

Fork springs are 43.5 x 497mm long and measure 0.47kg/mm with 7mm of preload.

ICS measures 2.2kg/mm

 

The Fx should be heaps softer smaller clamp kind of a crossover. The mid is stiffer maybe thats what he is feeling also not sure of the bleed posted on the FX if its the same post as the F model then its been removed 11's against the post. 

 

MM 

Edited by MartyMOOSE

Yup found them thanks for the help!

Hey Marty

 

Do you know what the stock fork oil quantity is on the 2014 yz250f ?

and do you find the quantity makes much of a difference?

The oil level effects the last 1/3 of the travel. I'll look tonight for the level, if it helps I run 330ml which is less than stock.

Edited by MartyMOOSE

Hey, Neighbour. 

 

I weight the same as you and also found the suspension to be too stiff for my intermediate-level skill. 

 

I have completely reworked my forks (did the job myself) and softened the shock spring by 10% and added a PivotWorks shock spring thrust bearing. 

 

4.0 kg/mm forks springs, lighter compression chamber springs, gold valve with RaceTech suggested valve stacks (softer), Ohlins #5 oil and fresh bushes and seals. Also fitted the billet compression reservoir pistons. 

 

Net result is a bike that does not throw me around at all now. The dreaded 'deflection has been eliminated and I have so much more confidence in the machine. I can push much harder. 

 

I did the work on the forks myself. It is fairly involved, but if you take your time, work through the on-line videos, study the service manual and have a Yamaha Tech handy to answer dumb arse questions, it is do-able. 

 

All of the details are over on this thread, but I am happy to answer any question you have. 

 

            #452            

 

Gaz. 

Does anybody have the shim stacks measured yet that they could post?

Here BFS forks only 2015 wr250f 

 

32.15x11

28,11

32.11x3

30,11

28,11

26,11

24,11

22,11

20,11

18,11

16,11

14,11

12,11

10.30x3  0.20

20,161

11.25x3

 

 

Mid

20.11 x 3

18,11

16,11

14,11

12,11

10,2 x 2

12,3

15,3

17,3

5.3 collar

Float 0.23

Harshness and stiffness are two entirely different things. You have have stiff or soft suspension which is harsh. Where is it harsh though? Deflection? On throttle chop? On the brakes? What about the rear shock? Sag numbers?

Thanks!

MartyMoose, 

 

Thanks for posting the fork stack data.   For the WR stacks, is that first line correct (32.15x11)?   Should that instead be 32.11x15? 

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