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2015 crf450 suspension

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Details released recently show that the 2015 crf450 is using the KYB psf2 fork. Claiming high and low speed adjustment for compression and rebound.

It appears that one fork is compression, one rebound, both with adjusters On the top cap. Does anyone have any more information/ideas?

Also the New shock has hi/lo compression and rebound mounted up top. How does this work, traditionally the rebound adjuster is Clevis mounted and is 'through' the rod bleed adjustment.

It is good to see some progression, stuff we have seen on factory bikes in the last couple of years coming through.

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I Havnt got any info. But I've noticed the same things as you. I was interested to how the reb adjuster works on the shock, similar to ohlins it has rebound at the top aswell I think. But it must still have a bleed through the centre of the shaft or maybe it's blocked off! really keen to see what it's like.hopefully it's valved for a faster rider stock!

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The shock does still have a bleed in the shaft but it is tiny compared to previous years. And the forks are quite a bit different inside compared to the 13-14 fork. The main compression stack is now back at the bottom of the fork. It kind of reminds of a 4CS fork a little. However, there is no metering rod down the middle of the damping rod. The rod is filled with oil and is by pressure is moved through the caps adjusters. Still have to tear down the rebound fork to find out the exact differnece between the two because so far they seem identical in valving, just like a 4CS. Both forks have a complete compression valve, a midvalve and rebound stack, I tore down the compression stack on the right fork but ran out of time to tear down the mid/rebound. And it has some interesting valving, quite the opposite in design compared to the last two years. Good stuff.

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The shock does still have a bleed in the shaft but it is tiny compared to previous years. And the forks are quite a bit different inside compared to the 13-14 fork. The main compression stack is now back at the bottom of the fork. It kind of reminds of a 4CS fork a little. However, there is no metering rod down the middle of the damping rod. The rod is filled with oil and is by pressure is moved through the caps adjusters. Still have to tear down the rebound fork to find out the exact differnece between the two because so far they seem identical in valving, just like a 4CS. Both forks have a complete compression valve, a midvalve and rebound stack, I tore down the compression stack on the right fork but ran out of time to tear down the mid/rebound. And it has some interesting valving, quite the opposite in design compared to the last two years. Good stuff.

Do you have the valve stacks at all, I'm keen to see how they look. Is the shock valving stiffer then previous yrs?

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Shock

reb

40-0.20*4
28-0.11*1
38-0.30*1
36-0.30*1
34-0.30*1
32-0.30*1
30-0.30*1
29-0.30*1
28-0.30*1
27-0.30*1
26-0.30*1
26-0.30*1

 

comp

44-0.20*10
42-0.15*5
40-0.20*1
38-0.20*1
34-0.20*1
30-0.20*1
26-0.20*1
24-0.20*1
22-0.25*1
21-0.30*1

 

fork

reb

26-0,11*3
13-0,11*1
10-0,11*1
19-0,11*1
16-0,11*1
14-0,11*1
13-0,11*1
12-0,11*1
11-0,11*1
10-0,30*2

 

MV (uses a LVSP MV system)

27-0,11*3
24-0,11*1
22-0,11*1
20-0,11*1
18-0,11*1
16-0,11*1
14-0,30*4
13-0,30*5
16-0,11*1
20-0,11*1
24-0,11*1
27-0,11*3

 

11-0,25*
6 mm

 

base

26-0,11*5
24-0,11*1
22-0,11*1
20-0,11*1
19-0,11*1
18-0,11*1
17-0,11*1
16-0,11*1
15-0,11*1
14-0,15*1
13-0,15*1
12-0,30*1

washer
12-0,25*3
20-0,11*3

 

oillevel 92mm (its an open chamber fork)

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Maybe because of less bleed via the main piston.
I dont know how big the bleed area is unfortunately.

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Shock

reb

40-0.20*4

28-0.11*1

38-0.30*1

36-0.30*1

34-0.30*1

32-0.30*1

30-0.30*1

29-0.30*1

28-0.30*1

27-0.30*1

26-0.30*1

26-0.30*1

 

comp

44-0.20*10

42-0.15*5

40-0.20*1

38-0.20*1

34-0.20*1

30-0.20*1

26-0.20*1

24-0.20*1

22-0.25*1

21-0.30*1

 

fork

reb

26-0,11*3

13-0,11*1

10-0,11*1

19-0,11*1

16-0,11*1

14-0,11*1

13-0,11*1

12-0,11*1

11-0,11*1

10-0,30*2

 

MV (uses a LVSP MV system)

27-0,11*3

24-0,11*1

22-0,11*1

20-0,11*1

18-0,11*1

16-0,11*1

14-0,30*4

13-0,30*5

16-0,11*1

20-0,11*1

24-0,11*1

27-0,11*3

 

11-0,25*

6 mm

 

base

26-0,11*5

24-0,11*1

22-0,11*1

20-0,11*1

19-0,11*1

18-0,11*1

17-0,11*1

16-0,11*1

15-0,11*1

14-0,15*1

13-0,15*1

12-0,30*1

washer

12-0,25*3

20-0,11*3

 

oillevel 92mm (its an open chamber fork)

So I was right, that the valving is the same on both forks. Since you beat me to it, what is it that differenciates the two forks, as far as the comp/rebound?

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I dont know, I havent seen one from inside. I only got the setups from a KYB guy.

 

But I guess its a checkvalve controlled rod or so.

Its quite easy to imagine how the comp adjusters work:
Oil goes through the rod (not only the tap as in the past) on comp stroke right up to the cap. The cap includes the two adjusters; one needle cadj (ls) and a blow of valve with spring (hs).
The oil will leave the cap and falls down into the outa chamber. since its a open chamber fork, this will work fine.

 

But on reb cycle... cant imagine that at the moment since the caps would suck oil and there is no oilbath up there haha

 

So there has to be something special about them in regard to that...

 

Maybe somebody could enlighten us?!

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I dont know, I havent seen one from inside. I only got the setups from a KYB guy.

 

But I guess its a checkvalve controlled rod or so.

Its quite easy to imagine how the comp adjusters work:

Oil goes through the rod (not only the tap as in the past) on comp stroke right up to the cap. The cap includes the two adjusters; one needle cadj (ls) and a blow of valve with spring (hs).

The oil will leave the cap and falls down into the outa chamber. since its a open chamber fork, this will work fine.

 

But on reb cycle... cant imagine that at the moment since the caps would suck oil and there is no oilbath up there haha

 

So there has to be something special about them in regard to that...

 

Maybe somebody could enlighten us?!

 

I'd suggest there could be modern style rebound adjuster with rod keeping the bypass controlled down inside the cartridge instead of using the older style compression side recirculating system. They may have needed to use the recirculating style on the compression side to get the oil up to the cap where they had more room to house the hs & ls adjustments. Just a guess...

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So the rebound fork leg will have a rebound midvalve and a rebound type base valve ?

All of the valve stacks and pistons, compression, midvalve and rebound are the same, just like a regular fork. Tomorrow I will tear down the rebound side to find the difference between the two

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I'd suggest there could be modern style rebound adjuster with rod keeping the bypass controlled down inside the cartridge instead of using the older style compression side recirculating system. They may have needed to use the recirculating style on the compression side to get the oil up to the cap where they had more room to house the hs & ls adjustments. Just a guess...

There are no rods in the cartridge rods, either side. Both circulate oil through the caps.

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I dont know, I havent seen one from inside. I only got the setups from a KYB guy.

 

But I guess its a checkvalve controlled rod or so.

Its quite easy to imagine how the comp adjusters work:

Oil goes through the rod (not only the tap as in the past) on comp stroke right up to the cap. The cap includes the two adjusters; one needle cadj (ls) and a blow of valve with spring (hs).

The oil will leave the cap and falls down into the outa chamber. since its a open chamber fork, this will work fine.

 

But on reb cycle... cant imagine that at the moment since the caps would suck oil and there is no oilbath up there haha

 

So there has to be something special about them in regard to that...

 

Maybe somebody could enlighten us?!

I'm going to tear down the rebound fork to find out the secret. As far as the cap goes, your pretty much correct except I didn't see any pop off style valve in the fork cap. The passage is effected first by the low speed needle, then it turns 90 degrees to "fall back in" as you say, then the high speed needle controls whats left. At least thats the way it looked to me.

 

Ask your KYB guy if they have any issues with air leaking out. When this was first brought to me, it supposedly had 35psi. When I checked it though it was 30psi. Thought it was owner error. But the same thing happened yesterday. Put in 35 at the shop, started the day at 35 at the track, rode for an hour or so, down to 30psi. Refilled back to 35 and it held for the rest of the day. I'll see what it is in the morning

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I'm going to tear down the rebound fork to find out the secret. As far as the cap goes, your pretty much correct except I didn't see any pop off style valve in the fork cap. The passage is effected first by the low speed needle, then it turns 90 degrees to "fall back in" as you say, then the high speed needle controls whats left. At least thats the way it looked to me.

 

Ask your KYB guy if they have any issues with air leaking out. When this was first brought to me, it supposedly had 35psi. When I checked it though it was 30psi. Thought it was owner error. But the same thing happened yesterday. Put in 35 at the shop, started the day at 35 at the track, rode for an hour or so, down to 30psi. Refilled back to 35 and it held for the rest of the day. I'll see what it is in the morning

Practiced (saturday) and raced (sunday) the whole weekend on my 15 CRF450, checked the air pressure between every moto, and 2X during the practice day, temps were in the high 40s in the morning to high 50s to low 60s in the afternoon. The throttle side (rebound) fork always stayed right at 35psi, the left (compression) fork on Sunday when it started to warm up, jumped to 37 psi the 3rd time I checked it that day when it was warmest out, strange that that fork changed and the other did not?

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Its quite normal for psi to increase, even on just one fork. Its unusual for it to drop 4 psi, especially after riding it. I'm going to chalk it up to pilot error. I checked the psi today and it was at 35, just as I left it on Sunday.

 

As for the differences between the forks, the rebound has 2 bleed holes close to the midvalve/rebound assembly where the comp side does not. The piston post on rebound is solid so oil is forced through the bleeds, the comp is hollow. Otherwise the forks are identical valving wise.

 

It didn't really click that these are open chamber forks till he mentioned it above. Back to the future, huh?

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When we say open chamber we normally talk about a fork that the oil is at zero pressure , these are pressurised forks so they are not open chamber in the true sense of the old style ones ?

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After 1mm of travel usage, there is pressure on the oil in spring style OC forks.

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