Fork Oil

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Reducing the airspace will reduce the nose dive without altering the ride settings.
Thanks for the tip but my airspace has already been reduced to 90mm per Klaus's recommendations and I want to see if I can find an ideal setup with the oil level I currently have. Its going to take awhile, there is already such an improvement over the OEM fork springs that it is hard to get motivated (in the 40-45 degree weather we have) to experiment with other settings.

 
mcrider007,

Rather than messing around with the settings to try to overcome the nosedive, it will be easier & take less time to reduce the airspace to 80mm. If you decide you don't like it just syphon it back out. That's the next thing on my winter's list when I get my bike back from the dealer. (The Yamaha field rep insisted on seeing the disintegrated T-bar threaded frame tab personally.)

dobias <_<

 
Rather than messing around with the settings to try to overcome the nosedive, it will be easier & take less time to reduce the airspace to 80mm.
Does reducing the airspace (by increasing the oil) reduce nosedive because the air has to compress more or because the increased oil level gives more compression damping?

 
Rather than messing around with the settings to try to overcome the nosedive, it will be easier & take less time to reduce the airspace to 80mm.
Does reducing the airspace (by increasing the oil) reduce nosedive because the air has to compress more or because the increased oil level gives more compression damping?
Increasing the amount of oil reduces the amount of air in the fork.. Air is compressable, oil is not. Less air is effectively a stiffer spring. Reduce air too much, and the fork will come to an arupt stop at full compression earlier, perhaps dangerously so.

 
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Increasing the amountof oil reduces the amountof on the fork.. Air is compressable, oil is not.  Less air is effectively a stiffer spring.
That is what I thought, I also thought that it was better not to use air as a stiffer spring because it rebounds too quickly.

Slightly different subject, I just took a ride and when I got back I measured the distance between the highest compression mark on the forks and the bottom of the lower triple clamp. Does anyone know much distance there is between the lower triple clamp and the fork seal when the fork "bottoms"? Will the seal go all the way to the triple clamp or will it stop somewhere before that?

 
mcrider007,

I expect Radman will correct me if I give any bad advise...

As long as you have any clearance until the worst conditions,(i.e., stopping hard & hitting a chuckhole, too) I'd say you're OK. If you tried to prevent bottoming under any & all conditions you'd have it too stiff for the rest of the time.

dobias <_<

 
As long as you have any clearance until the worst conditions,(i.e., stopping hard & hitting a chuckhole, too) I'd say you're OK. If you tried to prevent bottoming under any & all conditions you'd have it too stiff for the rest of the time.
I just jacked up the front end to get the wheel off the ground and there appears to be 140mm between the top of the dust seal and the lower triple clamp. If the Wilbers fork springs have 135mm of travel like the OEM springs, then it is possible for the dust seal to come within a 5mm of touching the triple clamp if the forks were to bottom.

I went for a normal ride today with some moderate, but not hard braking, and it seemed like the forks were compressing a lot under braking, but when I measured the dust seal marks after I got home they were 38mm under the triple clamp, so it appears that I was only using about 102mm of the available travel and a long way from bottoming since the forks are progressive. I think the suspension guides would say that I should be using even more of the available travel but the forks do not feel the least bit stiff the way they are.

 
I have searched and searched, and I can't find a better overview of motorcycle suspension than the Peter Verdone Designs page. It ain't perfect, but it is the better than anything I've found so far.

So. Here is a a link Clicky to some info on air space. No final answers but a good starting point for beginners like me.

Dobias, I believe that I have decided to move closer to what you are using in terms of vis (cSt @ 40c). Probably gonna try to get some where between 15 and 20 on that scale. May have to use something other than silkolene, but there are others and some are just as good if not better. Gonna do some shopping in Ft. Worth via the phone and see who carries what. Thanks loads for your input.

Rad, Thanks for the howto. I'm still going to be slow and careful when working on this stuff. Sure glad there is someone out there with your encyclopedic mechanical experience and knowledge. I may have to ask for more advice in the future. Ok I almost certainly will. I am still interested in how your bike feels with that particular oil when you can get some miles on it. I'm beginning to think that Fork Oil is really snake oil with more than a little voodoo thrown in.

The PVD site claims that you should agonize over fork oil choice. Then makes like the pointed man, who, being in possesion of points in every direction, varity, and size, said "A point in every direction is the same as no point at all."

Lots of information, not sure how helpful any of it is.

 
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You can buy the oil online.

I've used MX South for such items that are hard to find. If you can't find it in the catalog..call them.. they can get anything. And before you ask, no the oil is not dirt bike specific.

Race Oil:

https://www.mxsouth.com/silkolene/silkolene...uid_pro-rsf.htm

Normal Oil:

https://www.mxsouth.com/silkolene/silkolene...id_fork_oil.htm

Does anyone know much distance there is between the lower triple clamp and the fork seal when the fork "bottoms"? Will the seal go all the way to the triple clamp or will it stop somewhere before that?
No, it does not bottom. That would ruin your seals. There is still a gap regardless of suspension compression.

Everyone needs to remember that there are 6, count them 6 variables to our front end setups:

1.) Oil viscosity

2.) Oil height

3. ) Preload setting

4.) Rebound setting

5.) Compression setting

6.) Spring rate

This is just the available adjustments!

For any individual rider, the exact same settings are not going to be optimal for YOU. We weigh different amounts and load the front the front end differently. We brake and accelerate differently. We ride different types of road conditions and at different speeds. And of course, we all have a preferrence of how suspension should "feel". I like firm, but compliant, but to some it may feel harsh. But I guarantee I ride *A LOT* harder than the person that things my suspension feels harsh. So I demand a different feel to the bike (ie handling is more important to me than a luxury ride). Thankfully, you don't need to compromise that much anymore with good modern suspension.

All these factors contribute to a dizzying myriad of options to use. To make matters worse, changing one setting affects the other!

Example: Increase the spring preload (or spring rate), and the rebound will need to be increased to compensate for the spring. Meanwhile the compression may (or may not) need to be adjusted softer. Alter the oil viscocity and it changes the rebound and compression as well. You have to take all of these factors into account when making changes. Then you have to analyze exactly what changes should be done according to your unique riding situations and preferences.

The net result is the ONLY way you are going to find the right setting for YOU, the individual rider is to simply try different settings and really try to note how that change affected the ride, handling, and "feel". Don't just copy someone else's settings as a last word on the issue. Start with what someone your weight is using, then tweak from there. Afterall...YOU are not the same rider as the next guy.

With that said, I'm prety sure Klaus, a professional suspension tuner who has asked you plenty of questions about the above, would recommend what he feels to be good starting points. So stick with them. Then tweak from there. Especially oil heights, folks. DNFW them too much, you'll be terribly sorry when you blow the seals or cannot dial out harshness/softness because of a wrong guess.

God, I think I created a monster by putting that article out on FJRTech on fork oil changes..

:hmmm:

 
Yamahaulic,

All very good advise, but for the last one. Yes, Klaus is knowledgeable, but only knows that Wilbers has told him to use Wilbers 7 1/2w.

WTF is that in centiStokes?

Even wilbers won't or can't say.

"Buy Wilbers oil and you'll be happy."

dobias <_<

 
Yamahaulic,
All very good advise, but for the last one. Yes, Klaus is knowledgeable, but only knows that Wilbers has told him to use Wilbers 7 1/2w.

WTF is that in centiStokes?

Even wilbers won't or can't say.

"Buy Wilbers oil and you'll be happy."

dobias <_<
+10

Dang it, there needs to be some standard here.

And I will not use Wilbers oil now if it hairlips the pope.

Still planing to use between 16 and 20 cSt @ 40c with high temp stability.

Thanks Yamaholic,

Maybe I will buy online. Not going to do the change over this week anyway.

GRRRRRR. :angry:

 
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With that said, I'm prety sure Klaus, a professional suspension tuner who has asked you plenty of questions about the above, would recommend what he feels to be good starting points. So stick with them. Then tweak from there. Especially oil heights, folks. DNFW them too much, you'll be terribly sorry when you blow the seals or cannot dial out harshness/softness because of a wrong guess.
Better too much air space than too little. Fork seals should last damn near forever if properly maintained.

 
Better too much air space than too little. Fork seals should last damn near forever if properly maintained.
+1 on that advice. Start out low (100mm), then raise from there.

The viscosoty issue is a tough one to deal with. 7.5 W in one brand should be just as thick/thin as the next brand. But that's not the case.

So the solution is to stick with the same brand-try one weight, then the next fork oil change--try another if you cannot dial out softness/harshness using clickers and preload. Mixing seems reasonable to me (ie for 8.75weight) , but what does that buy you over one or two clicks of the rebound/compression? Probably not a great deal. Maybe to a racer..but to us??

You know, I totally forgot to mention another factor that will throw a monkey wrench in this. THE SHOCK! Yep, the shock settings affect the front end, too. Specifically weight distribution at cruise, on the brakes, and while corner carving.

Too little shock rebound and forks will dive more when braking You'll crank up the fork spring and/or compression to compensate, only to find that it does not dive now, but feels harsh over large bumps.

As far as brand, I've tried several on the FJR as well as other bikes (Bel Ray, Silkolene, Motul). If you want the VERY best you can get---contact MX Tech suspension. They blend their own mix. These guys are probably the best suspesnion shop in the country. They won't know what an FJR is, but I'm sure they can speak the centistoke language. I'm sure it's not cheap!

Personally, I'm suing Silkolene RSF-Pro 10W now.

Oh, and I have another tip for ya'll. Sea Foam makes a transmission flush that is compatible with rubber seals. Toss a few ounces in, mix with ATF or cheap forl oil, then work the forks up and down for a few minutes (with fork cap off, springs out). Then dump and flush with only fork oil/ATF. You will be amazed at the amount of crud that comes out after the flush.

 
jlw-lawsuit.jpg
 
Oh, and I have another tip for ya'll. Sea Foam makes a transmission flush that is compatible with rubber seals. Toss a few ounces in, mix with ATF or cheap forl oil, then work the forks up and down for a few minutes (with fork cap off, springs out). Then dump and flush with only fork oil/ATF. You will be amazed at the amount of crud that comes out after the flush.
Called Trans-Tune. Big load 'o detergent. Actually, I have found that with yearly changes, fluid doesn't look bad at all. And thats the way it should be.

tt16_3X.jpg


 
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Err..uh...yes...USING Silkolene. I'm a better suspension tech than typist :)
Thats ok, if I needed a typist I can find one of those at work.

I'm sure glad you guys are here. I would never get the kind of input out here in the sticks that I get here on the forum. Certainly speeds the learning experience.

 
Hi All I'm prob. going to get smoked for this question... but here goes...

This oil you guys talk about it is for the front fork/ springs right?

Not for the shock.

Should I run for cover?

 
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