Changes in suspension feel after break in

[racerxx276]

So I’m trying to figure out what changes has taken place in my stock Suspension after break in. Last year I had about 4 hrs on my new 07 YZ450f. Between 4 hrs and 20 hrs the suspension had perfect bottoming control. I could hit anything and no bottoming, front or rear.

After 20 hrs the forks began to bottom pretty hard. During the course of the year I’ve done my own oil/seals /bushing maintenance . I’ve used the stock KYB 01 oil. Still unable to return to that initial feeling of bottoming resistance. Anyone have any ideas what causing the forks to bottom so easily now? Could the valving shims be losing their

Stiffness after 20 hrs? My 06 yz450f suspension did the same thing the year before…

I'm currently changing the oil to Maxima light shock oil, which I believe grayracer is using, to see if there will be a difference.

My weight 190 lb with gear , which is close to the spring limit front and rear.

Any ideas?

[racer 813]

When changing your oil, stick with the stock 01 stuff for sure!!! Maxima is ok if you want to change it ALOT! It seems to break down much faster.

Blowing through the stroke can be fixed by changing up the mid-valve, unless you are too heavy for the springs. what do you weigh?

[racer 813]

Sorry! I read your post again and seen that you said your weght. It is my opinion that you could go up one size on your springs and be very happy!

[grayracer513]

When changing your oil, stick with the stock 01 stuff for sure!!! Maxima is ok if you want to change it ALOT! It seems to break down much faster.

First, Supension oil 01 is NOT the standard fill fluid in any KYB fork from '05 on. All of the twin chamber forks use "S1" fluid. KYB S1 fluid is $27/qt, and doesn't hold up very well. It is not particularly popular with many suspension people.

Second, over the year or so that I run fork fluid, the Maxima Light Shock Oil has held up just fine. There is no indication of any kind of break down or loss of fork performance with it.

That being said, there are a number of good options available in fork oil, and Maxima's 85-150 Fork Fluid (5wt, equivalent of "01") is one among many.

Concerning the problem at hand here, yes, the rider weight is at the high end of the limit, but not over by more than 5 lbs., if a all. The '06+ fork is very sensitive to oil level in the outer chamber, and some have noted significant changes in harshness/plushness, and/or bottoming behavior with oil level additions or subtractions as small as 5cc per side. You might try that.

Also, if you're just one of the faster guys, you could very well benefit from bumping the spring rate one step. If you are a serious racer, give some serious thought to a custom revalve.

[racerxx276]

Hey Grayracer, thanks for the feed back. I get my oil and bushings from Enzo. They had told me that their KYB 01 was the same as the S1 from yamaha. Guess not....

I current have 2 bottles of the Maxima light shock oil that I'm going to try out. If that doesn't work I'll order the S1. I change my fork oil every 20 hrs anyway and I don't mind paying the difference if it will give me that initial ride back...

As far as spring rates, I know I'm close and even had FC do a revalve twice on them before going back to stock.I was racing desert, MX , worc and some SX tracks last year. I found that while the stock forks didn't work great on somethings , they worked best (stock) overall for everything.

I did add 10 cc's to the forks and found that in order to affect the bottoming I had to give away some plushness in the mid stroke. Yes I know, Another sign that the spring rate might be too soft. which leads me back to why did

they work darn well when new? Must be the oil?

Enzo put heavier fork spring in my 08 , but I still haven't had time to dial it in with the 3 feet of snow on the ground. Heading to Ca in 2 weeks to do some testing before the first worc race in Phoenix . I'll let you know how the oil works..

[grayracer513]

Yamaha used to specify KYB suspension fluid "01" up until '05. Then they switched to KYB "S1". They aren't the same, but "01" can be used, all the same. For whatever reason, Enzo seems to be one of the very few who prefers genuine KYB fluid. Do you think their opinion is significant?

One thing most suspension gurus do seem to be in agreement on is that they don't like S1 very much. The change in the character of your forks is partly due to the change the fluid has undergone since it was new. Wait 'til you see what it looks like.

The discussions I had with several fork builders that lead to trying the Maxima 3wt brought to light the fact that the viscosity of the oil, within a reasonable range, is not really very important. This is because forks don't force oil through metered orifices, but use valves instead. Valves work on pressure differentials, and respond to thicker oil simply by opening farther to allow the same pressure balance. This is deliberate, and is done to make the fork behave consistently regardless of oil temperature. The difference in viscosity between, for example, cold 5wt and warmed up 5wt is greater than the difference between 5wt and 3 or 7 weight.

[racerxx276]

I changed out the fork oil on my 07 the first time( 20 hrs) . Its was some ugly oil that came out...I agree it was trashed. I guess my biggest problem was thinking o1 and S1 were the same.

I'd have to think that Enzo wouldn't use an oil that would affect their reputation.

I do know that the 01 doesn't break down as fast as the S1.

Interesting thoughts on the lack of difference in oil wt.

thanks for the info gray..

[mxracer206]

Most of these forks I have seen do have some nasty oil in them and also air in the cartridge. A good oil change does bring back performance as long as you do the inner chamber also. I am close to your weight and just set up an 07 YZ-450 for myself. You will probably like one step stiffer springs, I always felt like my son could have used them also when he was on the bike. Also the mid-valve is a little light on the 07, that is one thing Yamaha finally fixed on the 08 models, they come stock with a good mid-valve setting. I do use Maxima shock oil in my shocks but have never been happy with Maxima fork fluid it seems to have a lot of stiction. I have had good luck with the Silkolene 5wt and it is only about $10.00 a quart.

[grayracer513]

I changed out the fork oil on my 07 the first time( 20 hrs) . Its was some ugly oil that came out...

Mine looked like some kind of oil/mucus hybrid. New S1 looks nothing at all like that.

[rickallen124]

Enzo has said that they prefer the 01 to the S1. Maxima, Redline, Torco and silkolene all make good fork oil. RG3 uses the torco oil as do a few other suspension companies.

[racerxx276]

The fork/oil life of the S1 seems to be about 15-20 hrs. Not a very good oil to use if your a suspension CO. I'm sure a lot of guys go a whole season without servicing their forks. So it makes sense not to use S1 unless you do regular fork maintenance...

[Kasjok]

Any thoughts about valvoline fork oil?

[racer 813]

I have heard of some local suspension shops up here in northern calif using transmision fluid in suspension.

And I thought that the 01 and s1 was just the difference between the fork and shock oil that is used. I thought that is what Jacolyn at enzo told me?

[grayracer513]

And I thought that the 01 and s1 was just the difference between the fork and shock oil that is used. I thought that is what Jacolyn at enzo told me?

That was true prior to '05. That's one of the things that made me try the Maxima Light Shock Oil; it was the most direct equivalents I could find.

I have used ATF in the single chamber KYB's and it was OK in some circumstances. Dexron II and III are about 7wt. Max LSO is 3wt. No one could say exactly what S1 is. It's not on the label, and the experts say that suspension fluid often just isn't graded that way.

[albertaguy]

What is it about the Yamaha suspension that makes it so resistant to bottoming out. I had an 06 yzf250, then an 07 yzf450, and comparing with my 05 crf450 it was night and day. The crf was decent throughout the track and off road but if you ever went long and landed flat (basically bottomed out hard) it was always a teeth gritter with a few strokes of bouncing all over the place. And that was with $800 worth of suspension upgrades and set up. Both my yamahas were stock and I weight 180 w.o. gear, yet even if I landed hard they never really smacked and there was no bouncing around after, just one hard hit then smooth. There were a few things I didn't like but I've never said a bad word about Yamahas suspension.

[racerxx276]

From what I can figure out its the S1 that keeps the forks from bottoming.

Its the only thing that I didn't replace when I rebuilt the forks the first time.

I just ordered a couple quarts. Won't be able to see if indeed its the S1 thats keeps the forks from bottoming until I get out of the snow and down to Vegas to do some testing in 2 weeks.

Anyone else using the S1?

[grayracer513]

Beginning with the '04 fork, KYB uses progressive hydraulic bottoming control. In this regard, oil weight may make a difference, since such mechanisms usually do take the form of a diminishing control orifice. Still, the difference in the viscosity of one oil from cold to hot is much greater that the difference in going to the next grade.

[Kasjok]

Does anyone have an experiance with addinol fork oils?