Need advice, setting up the rearshock on -10/-11 YZ450F

21 replies to this topic
  • HRC

Posted January 18, 2011 - 12:51 PM


What a is the "best",recomended free sag / race sag for the new 2010 chassi ?

  • tech24

Posted January 18, 2011 - 01:12 PM


From what I've heard a little more than normal lid 110 -115. I have mine at 115 and it works great but I'm not the best test subject and am curious to others responses.

  • grayracer513

Posted January 18, 2011 - 02:03 PM


You should consider whether the sag is being increased over the standard figure of 90-100mm in order to improve the rear suspension operation or to alter the steering head angle to affect the handling of the front end in corners.

When all is said and done, I doubt that 10mm is going to make a great deal of difference to the rear, as long as the spring rate is right, and it still has at least 20mm of free sag. If you recall, we talked about linkages and the perceived "problem" the bike is supposed to have, which often works out to be nothing more than the fact that the handling is considerably different (much quicker and more willing to go where directed) than the previous models. The extra sag does essentially the same thing as would a lowering link, making the head a little shallower.

My advice is to do exactly what you most likely will anyway, and that is to listen to what people say, think it over, try a few things that you think will work, and decide for yourself how you like it.

  • sneipfmx

Posted January 18, 2011 - 05:14 PM



  • atropine

Posted January 18, 2011 - 09:45 PM


Like others, I have read that a lot of folks are liking it set up around 110mm. Mine turned out to be 112mm right out of the box, and I decided not to touch it. I think it is great, but I am not a great rider and I don't have a whole lot of time on the bike yet.


Posted January 19, 2011 - 06:24 AM


Out of the box I think i was right around 120+ maybe more, i have it written down at home, I changed it to 109, and i really don't like it, before my next ride I am backing it up to around 120, I also lost a bit of weight so it will need adjusting anyways. My rear just felt too stiff and front to soft and the balance was off after the change, whereas right out of the box the thing handled beautifully. one other thing I noticed is my skid plate makes noise I don't like when I come down hard on the rear end, At least I think that is what it is, but it adds to the hard feeling of the back end.

  • NE14MX

Posted January 19, 2011 - 06:59 AM


I've been thinking about posting my experience and set up for some time but have been hesitant as I've seen no one else try this. I am a 51 year old B rider who weighs 185 or so pounds. I have a lot of experience as I have been riding since I was 11 and raced a good many years along the way though no longer do.

Anyway here goes, I strated off using the stock and then MXA recommended settings. At 100mm of rear sag the bike would often knife in (oversteer) at advanced lean angles. I was allready running the fork caps flush with the top triple clamp so I dropped the rear sag to slacken the head angle. I went to 105mm. This worked to a certain extent. The oversteer was gone but the whole bike would wallow. This could somewhat be compensated through body positioning but once you got tired or out of position, the turning was a little inconsistent. Stiffening the shock helped the wallow but felt harsh in the bumps.

After reading MXA, I considered buying a rear link. I didn't like that the link could effect the rear ratio enough to require a heavier spring if you are borderline and possibly require revalving of the shock. Obviously this works for many people including pros but research here and talking to people at the track was less than overwhelming at such a high cost. In the end you were lowering the back end 10mm allowing you to run 100mm of sag and raise the forks 5mm allowing for different setups.

I then read about the 2011 KXF250 and it's preload adjustable SFF fork. I thought adding 5mm of preload would bring up the fork instead of lowering the shock. Of course using this tuning method has been around for ever but the new Kawasaki made it easier to play with and the reviews of this feature were very good.

I had 15 hours on the bike so the forks were due for an oil change anyway. I used Amsoil in the cartridges and Mobil 1 0W20 in the outer chambers (355cc). I placed 1 3mm and 1 2mm preload washers (total 5mm) between the fork spring crown and retaining ring on the cartridge. These were from a set of springs I bought for my 2004 Honda and fit perfectly. I raised the shock back to 100mm of sag and am running the clickers at stock settings.

This has worked temendously for me. The forks are much more controlled and remain plush, yet have better bottoming resistance than stock. This is because the increased preload raises the front end 5mm and doesn't feel stiffer initially but when bottomed increases the force required by 10.34 pounds.

.47kg/mm X 2.2(lbs=kg) X 5(mm) X 2(springs)= 10.34lbs

in comparison one rate of stiffer fork spring would add

.01kg/mm X 2.2(lbs=kg) X 24.5 (mm=inch) X 12.2(inches of travel) X 2(springs) = 13.15lbs

I am really liking the handling of the bike as well as the suspension now. The bike turns well and consistently and I can quicken up the steering by raising the forks if a want and still have the option of dropping the rear sag for stability in sand, etc.

As a final note I changed from the stock 120X80 tire (96mm sidewall height) to a 110X90 Dunlop MX51 (99mm sidewall).

  • grayracer513

Posted January 19, 2011 - 07:59 AM


Some comments on that:

First, "knifing", where the front of the bike turns in farther or more suddenly than you intend, is not oversteer. Likewise, "tucking", which is like knifing except the the leading edge of the front wheel actually pulls the steering farther inward than the rider input, is also not oversteer. Oversteer is when the rear wheel looses traction in a corner before the front, and produces a "tail out" cornering attitude.

Second, changing the preload of any spring never makes it stiffer or softer, it only changes the height at which the bike will sit.

IMO, almost no one would be able to tell the difference in the 5mm preload change to the front fork except perhaps in the steering. The change in bottoming resistance was much more likely a product of your use of the heavier M1 0w-20 in the outer chambers, especially when you used so much of it. Amsoil Shock Therapy is one of the better conventional suspension oils available, and using it in the cartridges will be a noticeable improvement over the factory fill, even on a brand new fork. It probably does resist bottoming more, but I'm pretty sure that your cause/effect analysis is a little off.

In the event that you thought it needed a shallower head angle, I do agree with the approach of raising the front rather than lowering the rear much beyond 110, though.

  • luckyguy19

Posted January 19, 2011 - 08:17 AM


If you want to add a link to lower the rear of the bike, you can use the link off a 2007 WR450. It will lower the rear of the ike 11mm and be alot cheaper than an aftermarket link.

  • NE14MX

Posted January 19, 2011 - 08:39 AM


Well Grey, I may not have the handling term correctly but anyone who has ridden the 2010-2011 YZ450F knows the handling trait I am talking about. Let's just say I'm not alone in trying to tune the handling by dropping the rear end. Though this brings about it's own set of problems. So I am suggesting raising the front.

Secondly, 355cm3 is the stock amount of oil according to my manual. I thought this would be a good starting point and can easily be changed.

Thirdly, I agree the spring preload does not make the spring rate stiffer. It does cause the front end to sit 5mm higher but also the extra 5mm of compression at bottoming requires additional force as I calculated out. This is because at full compression the spring will have compressed 5mm more than before.

Finally, I began using Mobil 1 0W20 in my CRF450R forks years ago after reading about it in the Honda forum on TT and other sources. I believe it's base weight of 0 is actually lower than most 5wt fork oils. I would change it annually and besides the reduced stiction, the teflon guides were like new after 6 years of use.

I guess all I'm saying to people is to try 5mm of preload on their forks and set the sag at the usual 100mm. It costs about nothing and can easily be taken back out.

Please let us know your results.

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  • NE14MX

Posted January 19, 2011 - 08:45 AM


Lucky, thanks, I saw that thread and pasted it into my long term folder. It was especially helpful for having the part numbers here it is;

5XC-2217F-90-00 ROD, CONNECTING 1 $51.12

93315-32269-00 BEARING $9.08 2 $18.16

93109-22019-00 OIL SEAL $8.63 2 $17.26

90387-14009-00 COLLAR $7.87 1 $7.87

That is all the parts needed to make it work, depending on local prices should be around $100 total.

I asked some time ago in the suspension forum if anyone did the cross checking of other year and model bikes for the length of the suspension link. However, in the above post are some of my reservations for going this
way. (mostly cost)

  • grayracer513

Posted January 19, 2011 - 10:10 AM


Mostly, I have no real problem with what you posted, and I'm simply trying to clear a few things up. As far as the handling trait you complained of, as long as it's not actually causing the bars to be pulled in toward the apex, most RM or RMZ riders would consider that an attribute, rather than a fault, and the reluctance of the older YZF's to do anything like that has been most people's biggest complaint about them right along. If it just steers very quickly with relatively little input, I'd think that one would rather get used to it. But again, if it's causing the front to tuck under and pulling the bars in, that I would call a fault.

As to oil level, most people who have played much with the KYB SSS fork on the YZ's have found the suspension too harsh when filled to 355ml. I know that's the spec, but all the same. I use around 320ml in mine, and while that doesn't sound like a big difference, the fork is actually quite sensitive to this change, and you can feel it. Another thing that plays into this is that I have drilled the free piston to interconnect the air space above it with the outer chamber. ( See "Free Piston Mod")

Regarding the oil weight, the grade 0w-20 states that the oil has an SAE motor oil viscosity of 0 at 40 ℃, and 20 at 100 ℃. In the specific case of M1 0w-20, the viscosity at 40 ℃ is reported at 60 cSt. That's about the same as Bel-Ray Fork Oil in 15wt, PJ Fork Tuner 20wt, or Motul Factory Line 15-20. It's a fairly heavy oil at base operating temperature, and gets effectively thicker (relative to other oils) as it gets hotter. That is, as the temperature climbs, it becomes more and more like a 20wt, even though the oil actually thins out. So don't kid yourself, it's not a thinner oil than specified.

But as it turns out, it's a good trick anyway. Because the bottoming is controlled by oil locks, the heavier oil adds bottoming resistance even while you lower the oil level to reduce the effect of the "air spring" (the compression of the air trapped in the fork). I use the 215.VM2.K5 oils from SMART Performance in mine, using the lighter grade in the cartridge, and the heavier in the outers, same as you. Works well, BUT... if you do run deep into the stroke a lot, be aware that the extreme pressure the cartridge seal is exposed to during bottoming can cause outer chamber oil to be forced into the cartridge, and this can cause some mixing of the two fluids over time in both chambers.

The reason that I don't think that the 5mm additional stroke you picked up will be felt as significant extra bottoming resistance in and of itself is that on a percentage basis, it just isn't much of a change. It IS unarguably 10+ extra pounds of spring compression, but a pair of .47's preloaded 20mm (for a rough number) already has over 680 pounds of force on it when compressed 12.2 inches, so the extra 10 is only an additional 1.4%.

But as sensitive as the bike is to geometry changes, it could very well change the steering noticeably.

  • alien

Posted January 19, 2011 - 01:45 PM


In my 2010 I use .49 fork springs , 12oz. of 5w20 oil in the outer chambers and the tubes in the stock position. In the rear I have a 5.2 spring set with 4.5" of rider sag and stock linkage. I weigh 215 and this kind of balanced it out.

  • motojase316

Posted January 20, 2011 - 04:18 AM


This is my set up 10 and 11. from my tuner after valving was done

Spring: 5.3 (stock is 5.5), preload: 11mm, sag: 105mm, oil wt: 3wt
Compression low speed, mx 10 clicks out, sx 6 clicks out
Compression high speed mx: 0 turns in, sx 1/2 turns in
reound mx: 12 clicks out sx:10 clicks out

Yeah so back to the question.... 105mm, works good...


Posted January 20, 2011 - 06:30 AM


ya true grayracer, but maybe the back end being up that much higher than the front gave me that illusion, it just didn't feel right. Ideally i need stiffer front springs, but I'm going to wait till my bodyweight drops a bit more before messing with it.

  • HRC

Posted January 20, 2011 - 12:36 PM


Just mounted some gold on mine today....B)

Set the race sag at 103mm, will see how it works out. But probably need to adjust it after braking it in.

Can´t wait to try it out !:smirk:

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  • tech24

Posted January 20, 2011 - 12:44 PM


Just mounted some gold on mine today....B)

Set the race sag at 103mm, will see how it works out. But probably need to adjust it after braking it in.

Can´t wait to try it out !:smirk:

Posted Image
Posted Image

Anyone ever tell you that you SUCK! :busted:

  • HRC

Posted January 20, 2011 - 12:48 PM


Anyone ever tell you that you SUCK! B)

Me !?:smirk:....Naaa ! :busted:

  • tech24

Posted January 20, 2011 - 01:27 PM


Sure is pretty let us know how it works

  • motojase316

Posted January 21, 2011 - 03:23 AM


HRC let me know if that shock is a good thing, I am about to spend some serious $$$ on the shock to match the factory front end, this could be an option.

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