2011 yz450 suspension


19 replies to this topic
  • ccie2be

Posted July 31, 2011 - 09:19 AM

#1

Had my 3rd ride last night on my scooter. Replaced the front springs to balance the front and rear and right away I was jelling with the new bike. It had a stink bug feel the first two rides. I highly suggest getting the springs mated ASAP.

  • rickallen124

Posted July 31, 2011 - 12:24 PM

#2

what spring rate did you go with on the forks?

  • ccie2be

Posted July 31, 2011 - 03:58 PM

#3

I weight 195 so I went with a .49 rate. Its a completely different bike. :smirk:
What do you weight?

  • phiderman

Posted July 31, 2011 - 05:22 PM

#4

i weight 195 also and i got a .49 front and 5.9 rear as per factory connection and the bike works perfect with about 105mm of sag and mxa clicker settings

  • rickallen124

Posted July 31, 2011 - 08:37 PM

#5

I'm 190-195. I've had it revalved and that made a big difference. I thought about going with the .49 in the front but my tuner told me that they tested the stock springs and they were really close to .49 so there wouldn't be that much of a difference. Maybe the .49 kyb springs test closer to .50.

  • phiderman

Posted July 31, 2011 - 09:01 PM

#6

i switched to the 5.9 rear cause i couldnt get the sag within 100 - 105mm. after that i noticed the forks bottoming so i switched to .49 factory connection fork springs and now the bike is perfect.

  • Kawirider37

Posted August 01, 2011 - 12:19 AM

#7

Are you running an after market rear link (pull rod)?

  • ccie2be

Posted August 01, 2011 - 03:24 PM

#8

I'm 190-195. I've had it revalved and that made a big difference. I thought about going with the .49 in the front but my tuner told me that they tested the stock springs and they were really close to .49 so there wouldn't be that much of a difference. Maybe the .49 kyb springs test closer to .50.


Things can be tuned(revalved) with stiffer or softer springs but with stock valving you have to get the balance between the front and rear stabilized.
47s are stock on the front.

  • ccie2be

Posted August 01, 2011 - 03:25 PM

#9

i switched to the 5.9 rear cause i couldnt get the sag within 100 - 105mm. after that i noticed the forks bottoming so i switched to .49 factory connection fork springs and now the bike is perfect.


Yep, all about balance. The manual say 90-100mm of rear sag and i tested this weekend about about 100-101 with really good results.

  • ccie2be

Posted August 01, 2011 - 03:27 PM

#10

Are you running an after market rear link (pull rod)?


Hey, not sure if you were talking to me but I'm not. I feel most people use those for lowering purposes.

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  • phiderman

Posted August 01, 2011 - 03:33 PM

#11

i am not using the link and i have my sag set 102mm right now. i like the feel and balance right now.

  • Kawirider37

Posted August 02, 2011 - 08:05 PM

#12

So for those that are not using the aftermarket links: You're not having any issues with the front wheel knifing in? If not please go into more detail on what front tire you are using and what type of dirt your riding.

Sorry for hijacking the thread.

  • polarbear

Posted August 02, 2011 - 08:19 PM

#13

I am 215 and I got the 6.0 rear shock and was told by Factory Connection to go with the .49 forks. I ride motocross so this makes me wonder why all of you who are at 195 were told to use .49's as well. Seems like I should be at the .50 mark. I dunno...

  • phiderman

Posted August 02, 2011 - 09:09 PM

#14

factory connection told me .49 and 5.9. Also no knifing of the front end. i did initially when i bought the bike but when i stiffened up to front end it made the bike awesome. i could be wrong but knifing is usually a case of too much weight on the front end, ie forks too high in the clamps, springs too soft, or fork oil too low. my forks are 4mm over with 350cc of oil and .49 springs.

  • Quernix

Posted August 02, 2011 - 11:26 PM

#15

I am 220lbs w/o gear and run 5.0 and 60 N/mm springs. This leads to 30/102mm sag. More sag leads to wallowing and discomfort imo. I run the forks about 2mm lower than flush (cap slightly in triple clamp). 360ccm oil in the forks. SKF HD seals. Maxxis IT tires.

With this balance the bike is very cornerhappy and well planted on the front wheel. No knifing and the right amount of oversteer. For my tase and the tracks I usually ride it feels agile and well balanced. For sand I will drop the fork even further. IMO the link come into play when riding mainly sand or for really fast tracks. I am scared to use a link, since it could change the anti-squad characteristics - that I really like on the bike.

When the bike was new I felt that kicking from the rear that some have reported. But after brake-in and playing with the klickers (I run stock with slighly slower rebound) it is barely noticeable anymore. The stock valving is stiff (the shock more than the fork). I can imagine lighter riders try to find a solution with the link, where the valving is the cause.

With my 220lbs I have never been happy with the stock valving of my bikes. After 15hrs on the YZ I still do not feel the need for a revalve - which is great!

  • grayracer513

Posted August 03, 2011 - 06:50 AM

#16

i could be wrong but knifing is usually a case of too much weight on the front end, ie forks too high in the clamps, springs too soft, or fork oil too low.

Knifing is caused by a too steep head angle, which causes an excess of negative trail when leaned over and cornering. The causes you list can lead to that, but aren't directly the source of the problem. In the older YZ's, for example, those same things are deliberately done in pursuit of eliminating the excessive understeer those bikes have. With the new ones, which don't have that problem, it works against you rather than for you.

When the bike was new I felt that kicking from the rear that some have reported. But after brake-in and playing with the klickers (I run stock with slighly slower rebound) it is barely noticeable anymore.

Typically, the rebound curve of KYB shocks as delivered on YZ's is way too slack in initial response. It causes the rear to kick off of peaks, skip left and right, and destabilizes the front end. Slowing that with the clickers helps, but not nearly as much as actually restacking the rebound valve with stiffer face shims does. The improvement is pretty remarkable.

  • phiderman

Posted August 03, 2011 - 08:23 AM

#17

[quote name='grayracer513']Knifing is caused by a too steep head angle, which causes an excess of negative trail when leaned over and cornering. The causes you list can lead to that, but aren't directly the source of the problem.

Thanks for the clarification. I guess thats what i was getting at, I just didnt consider that you could theoretically have a problem with knifing the front end; like some bikes do; and have none of the issues i listed. Also i run a MX51 front and rear tires.

  • Kawirider37

Posted August 03, 2011 - 02:00 PM

#18

thanks for all the input.

  • Quernix

Posted August 04, 2011 - 12:01 AM

#19

Typically, the rebound curve of KYB shocks as delivered on YZ's is way too slack in initial response. It causes the rear to kick off of peaks, skip left and right, and destabilizes the front end. Slowing that with the clickers helps, but not nearly as much as actually restacking the rebound valve with stiffer face shims does. The improvement is pretty remarkable.


Grey, would adding two 40 .2 (from 4 to 6 face shims) to the shock rebound stack solve the problem in you opinion? Even with the 60 N/mm spring?

Since you seem to know your stuff, do you have any suggestions to make the initial stroke of shock and fork compression a bit plusher while keeping the characteristics of the stock low and high speed compression dampening?

  • grayracer513

Posted August 04, 2011 - 07:04 AM

#20

The original rebound stack in my '06 shock had 14 36x.15 shims in it. Working with SMART Performance, I replaced the first 7 of these with 36x.30's, which is a considerable bit of beefing up, as a .30 is a lot stiffer than two .15's are. I had my doubts before hand, but the improvement was immediately obvious the first time I attacked a set of whoops with it. The approach is a little controversial among more traditional tuners, but it works. Definitely works.

I've seen a build sheet Dave did for a '10 YZ450. The '10 uses .20mm shims on the face of the RB, so not so many are required, and by the looks of what he did with that one, they don't need as much as the older bikes. There, he replaced the first 3 with 40x.30's and let the rest of the rebound unchanged. His compression stack was (changes in bold):

(8) 44x.20
36x.15
32x.15

44x.20
44x.25
42x.20
42x.25
40x.20
38x.20
followed by the rest of the stock stack

The fork set up I'm using is Dave's "Del Taco" setup, which modifies the mid valve to a clamped, pressure limited type of thing, so it what I did with mine doesn't relate directly to a normal design. Generally, what you're asking about is accomplished by the use of a "crossover" in the compression stack. That is a smaller diameter shim or shims in mid-stack that allows the face shims below it to lift a small amount with less resistance until they come into contact with the rest of the shim stack above the crossover as the flow velocity increases. How much smaller the shims are than the shims under them, how thick the crossover is, and where in the stack it is placed all bear on how it affects the damping curve. The 36 and 32 mm shims in the stack above are an example.

When you're looking for small bump or washboard plushness in the fork, remember that a too stiff rebound can work against this. The fork needs to recover quickly enough so it doesn't get drawn down in the stroke, raising the spring pressure for the successive bumps.

I'm not what I consider a suspension expert. Spend some time in the suspension tuning forum and you can pick up quite e bit there.





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