2014 yz450f rear suspension tips?


20 replies to this topic
  • yzUSMCf

Posted April 13, 2015 - 01:30 PM

#1

Im about 205 in gear my suspention is stock. I feel like my forks are dialed in at 335 cc oil and 14 comp and 6 /8 rebound no bottoming issues front or rear now it feels good on jumps and most of the track . But when I go down a particular slight down hill high speed straight section that has some bumps and bunny hill jumps the rear seems to dance and swap a little on hard edges and I loose confidence and that's were I get passed ! My rear sag is 105 high speed 2 turns out low speed 15 clicks out and rebound is 10 clicks out. What have you guys learned works?? I'm also trying to get the bike to turn in and hold a rut better. These settings are were I left off last time I rode

any suggestions?Thanks!

  • GHILL28

Posted April 13, 2015 - 06:12 PM

#2

Your HSC is basically all the way out, that's the big issue I see with it.  Try 1/2-1 turn out.  The 15 out on low speed looks like an awfully loose setting as well.

 

I'm about your weight all geared up and I run HSC 3/4, LSC 12 (10 in some cases), R 13.  106mm sag.  If I run the HSC much further out the cornering goes to hell.



  • yzUSMCf

Posted April 13, 2015 - 07:43 PM

#3

So you set your hsc to harder than the stock setting? I figured 2 would be fine I started off trying to mimic what motocross action mag did on there test bike. Your settings are quite different than mine I could give it a go I've never ran HSC less than 1 1/5 so It may benefit me. It Does make sense that it would improve handling . Are your forks flush with the triple clamp?? Thanks for the reply!

  • yzUSMCf

Posted April 13, 2015 - 07:46 PM

#4

I remember when I set HSC out to 2 turns was because the bike was harsh on to flat hard landings or if i came up short ,at the stock 1 1/5 out.

  • GHILL28

Posted April 13, 2015 - 07:50 PM

#5

Forks flush.

 

I run the HSC even further in for more aggressive MX stuff.

 

In reality it's not even a "high speed" adjuster, it's a "high load" adjuster, and that can come from acceleration squat, cornering loads, jump takeoffs, etc.  Completely changes the attitude of the bike.  

 

My only big hangup with the bike is the midstroke harshness of the forks.  They seem to hit a wall right in the midstroke, and even low oil isn't tuning it out, like 320cc and I still have 1/3 travel left after some fast whooped out offroad stuff and I'm 185lb on the stocks springs.

 

Edit:  That, and the brakes &%$#@!ing blow.


Edited by GHILL28, April 13, 2015 - 07:50 PM.


  • grayracer513

Posted April 14, 2015 - 06:57 AM

#6

 

In reality it's not even a "high speed" adjuster, it's a "high load" adjuster, and that can come from acceleration squat, cornering loads, jump takeoffs, etc.  Completely changes the attitude of the bike.  

 

Sorry, this isn't true.  Compression damping of any kind has the effect of holding the bike up, but only by slowing the rate of compression.  Only the spring carries any actual load. 

 

The term "high speed" in suspension damping refers to the speed of the stroke. The HS circuit becomes effective only when the stroke speed has become high enough that the flow through the low speed circuit has become great enough to raise the oil pressure to the point of operating the HS valving.  Jump take off faces are usually considered "low speed" events, while the landings are high speed.  Hitting whoops is "high speed".  Hitting a 4" rock at 15 MPH is high speed, too. 

 

Below is a typical KYB  compression adjuster assembly.  The top picture shows a low speed condition. Oil comes from the main piston and part of it flows as bleed oil down the center of the exchange valve stem past the LS adjuster needle and to the bladder.  Oil flow that exceeds the capacity of the bleed circuit lifts the larger 4 shims at the exchange piston, which are then actively managing the damping rate. 

 

As the stroke speed increases, the shim stack bears against the smaller shims at the base of the stack hard enough to push the spring seat collar back against the HS adjuster spring.  The preload on this spring is what is controlled by the HS adjuster, so it directly affects how much deflection of the larger shims in the stack is required to deflect the smaller, high speed section of it. 

 

If you have the tail end skipping out like you mentioned on a YZ, it's almost always a lack of rebound control.  They're pretty notorious for it, and beefing up the face of the stack is really the only way to fix it.  The problem with using the rebound adjuster on the typical YZ to tighten the damping up is that once you get the high speed rebound behavior under some control, the lower speed rebound events are way over damped due to a lack of free bleed past the adjuster needle, and that also upsets things on the compression side.  Nevertheless, if you're at 12 out on your rebound, take it down to 8 and see if that helps with the skipping. 

 

highspeedUnitLS-HS-1_zpsd225380f.jpg



  • GHILL28

Posted April 14, 2015 - 07:58 AM

#7

You're changing the cracking pressure on the valve that works only off displacement with the HSC adjuster.

Go test it with a stock adjuster. Use a stock LSC and R setting, then tell me that a half turn of the HSC doesn't dramatically affect those load scenarios.

  • grayracer513

Posted April 14, 2015 - 08:46 AM

#8

You're changing the cracking pressure on the valve that works only off displacement with the HSC adjuster.

Go test it with a stock adjuster. Use a stock LSC and R setting, then tell me that a half turn of the HSC doesn't dramatically affect those load scenarios.

 

But I have.  I've also reshimmed the exchange stack to be lighter.  I know what it does.

 

The HS adjuster does not modify the initial opening pressure of the exchange stack.  That function is handled by the LS needle.  The HS is a true HS-only adjustment.



  • GHILL28

Posted April 14, 2015 - 08:50 AM

#9

Right, that's why I said the STOCK stack.  I found that gutting the Cadj stack with the SPI kit turned the rear shock to mush in all conditions, because it didn't put any pressure on the main stack and broke at such low pressure itself.  The adjuster never worked the way it was supposed to with the light setup.  Maybe if the collar were loading shims further away from the clamp you'd get the proper adjustment back, but not with the stock collar.

 

Stiffer stacks there work well actually, even for desert..



  • grayracer513

Posted April 14, 2015 - 09:04 AM

#10

I didn't use an SPI kit for the exchange stack.  Stock spring, two thinner shims.  Whatever you believe you found with the kit, look at the exchange valve again.  Understand first that neither the exchange piston nor the exchange valve stem move during operation because the exchange piston is clamped in place by the combination of the adjuster housing and the sleeve it bears on.  Displaced oil flows first through the bleed circuit controlled by the LS needle, then, as pressure rises, opens the exchange stack, then finally begins to compress the HS spring.  The HS spring serves to bolster the two small shims in the HS section of the exchange stack. The HS mode only comes into effect once the bleed and LS stack has been overwhelmed. 

 

And, again, the tension on the HS spring does not affect the opening pressure of the exchange stack in any way.  Only the LS needle does that.



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  • GHILL28

Posted April 14, 2015 - 09:26 AM

#11

Yep, I get how it works, but effectively increasing the clamp diameter to a larger one (for a longer range of pressures by adding preload) does change the overall stack stiffness.  Mechanically, the shimstack doesn't behave any differently than a spring/poppet valve with a slightly variable rate to it.



  • yzUSMCf

Posted April 14, 2015 - 11:06 AM

#12

I'll play with the rebound atleast to mellow out the rear end some.i suspect that because my hs and ls are at the softer setting I'm not mistaking the kick as too much compression. As far as my adjuster settings go am I in the ballpark? ( + or- a few clicks) or does it look like i am way off on comprehending how to tune suspension? You guys seem experienced with suspension!

Edited by yzUSMCf, April 14, 2015 - 11:10 AM.


  • Phil Hannah

Posted April 14, 2015 - 01:10 PM

#13

6 out on fork rebound seems like to much. Could forks be packing?



  • GHILL28

Posted April 14, 2015 - 01:40 PM

#14

The front end feel is REALLY light on these bikes.  They seem to like a tighter rebound up front to keep a good arc past the apex of the corner, even though it can cause packing elsewhere.



  • Phil Hannah

Posted April 14, 2015 - 02:19 PM

#15

The front end feel is REALLY light on these bikes.  They seem to like a tighter rebound up front to keep a good arc past the apex of the corner, even though it can cause packing elsewhere.

I have the 15 so that's a variable with fork reb  8-10 out and bike turns incredible with settings close to OP in rear of my bike with more sag.



  • GHILL28

Posted April 14, 2015 - 02:43 PM

#16

Ah, yep, running the stock spring?

 

I'm 8-9 out with the stock 2014 spring.  185# + gear.  6 does seem a little on the slow side, but maybe not for a lighter rider who needs some more "stick".  OP said he's 205# though..



  • yzUSMCf

Posted April 15, 2015 - 07:58 AM

#17

6 out on fork rebound seems like to much. Could forks be packing?

yes stock spring .going from 8 to 6 on the rebound I didn't notice much of a difference so I kept it at 6 for now. I haven't noticed any packing though I'm a decient vet track rider that may be why. I'm still playing with adjustment to see what works best for me.

Edited by yzUSMCf, April 15, 2015 - 08:00 AM.


  • yzUSMCf

Posted April 15, 2015 - 08:04 AM

#18

yes stock spring .going from 8 to 6 on the rebound I didn't notice much of a difference so I kept it at 6 for now. I haven't noticed any packing though I'm a decient vet track rider that may be why. I'm still playing with adjustment to see what works best for me.

I noticed when I would over clear to flat the front would hop off the ground so I slowed down the rebound to alviate that I didn't change the comp because I felt it compressed well on the initial hit,but it would bounce back to fast.

  • yzUSMCf

Posted April 15, 2015 - 08:07 AM

#19

The front end feel is REALLY light on these bikes. They seem to like a tighter rebound up front to keep a good arc past the apex of the corner, even though it can cause packing elsewhere.

yeah I noticed with faster rebound when I would come into a rut fast and hard after the suspension would compress it sprung up preventing me to stay in the rut by standing the bike upright .

  • yzUSMCf

Posted April 22, 2015 - 02:21 PM

#20

So i changed my fork rebound from 6 to 8 and the shock rebound to 10 from 12 and I left the sag at 105 and the high speed at 2 and also slid the forks up about 3mm . It seemed to work well held a rut a little better and the rear end seemed to be more stable. It's tricky to tell what works at times because of track conditions changing from each ride. I think it's mostly my riding technique is at fault lol





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