changing fork oil

[pbraido]

Was wondering if anyone has changed the fork oil without pulling the forks off the bike and what the proper amount of fork oil is. I have drained it and was in the process of removing the top off the fork but before getting into this was wondering if it is done that easy as removing the top and filling. P.Braido

 

[evil_henchman]

You're asking for trouble. Do it right or don't do it at all. Directions are here.

 

[Ignacio]

The process is well documented here, but also hints strongly at getting the service manual for specifications that would be unique to each year.

 

[Geezer]

I thought about doing it without pulling the tubes off. I think you can drain the old stuff out through the bungs where the adjusters are in the bottom of each tube. The only way I could think of to determine how much to put in would be to measure what came out and replace with an equal amount. That assumes you haven't lost any past the seals over time.

However, I decided to replace the springs so I pulled the tubes to do the job and found that it is really easy to pull the tubes off so I would recommend you go that route rather than try to drain and fill them in place. With the tubes off you can get all of the old oil out, flush the valves, and measure the height of the replacement fluid in the tube so you know you put in the right amount.

 

[slapnpop]

I am by no means advocating this method...

That being said, regardless of what angle the fork tubes are at, the fluid level is always the same at the center of the tube. As long as you can measure the height at the center of the tube, it will be accurate at any angle (until you start pouring fluid out).

Even if you can drain out the bottom hole, I think you'll get a lot better flush by removing the forks and letting them drain upside down. If you're going to change the fluid, you might as well change ALL the fluid.

 

[FJR919]

Absolutely take the fork legs off. The previously mentioned articles give a good description. Whatever you do, make sure the the top triple clamp is loose before you remove the fork cap. Get enough fork fluid to flush them out a couple of times. I did mine at 8000 miles and I'm glad I didn't wait any more given the color of the oil and the junk that came out.

 

[evil_henchman]

The fluid that comes out after a few thousand miles invariably looks like shit. I think it's babbitt bearing material from the bushings. Yamaha recommends that the bushings (metal slides in the parts diagrams) be replaced any time the forks are apart as well as the oil and dust seals. It cost's all of about $50 to replace all the seals and bushings in both forks and it's a really good idea.

 

[FJR919]

The fluid that come out after a few thousand miles invariably looks like shit. I think it's babbitt bearing material from the bushings. Yamaha recommends that the bushings (metal slides in the parts diagrams) be replaced any time the forks are apart as well as the oil and dust seals. It's cost's all of about $50 to replace all the seals and bushings in both forks and it's a really good idea.

I agree the cost of the parts is minimal, but there is a big difference between flushing the fork oil and changing bushings and seals. The poster was concerned about removing the forks- I don't think a person that has reservations about removing the fork tubes is going to start taking them apart. Without experience working on forks and proper tools, I would advise against it.

 

[markjenn]

Guys, it's really not that hard if you're just changing the fork oil. You remove the forks as you'd remove then on virtually any bike, take the top cap off, drain the old oil out, refill with the proper amount of new, check the level, and put the forks back on. Unless you're removing the inner damper rod, there is no need to replace anything. It's not that big a deal. You're just pouring out the old oil and adding new. That's it.

- Mark

 

[Fred H.]

If you really want to get all the old fluid out, you should remove the damper cartridges and pump them to purge them of fluid, though this can be done without removing them (see page 4-80 of the manual). Once drained, you can refill them with fresh oil simply by inserting the bottom in an open container of clean fork oil and pumping, or if they are still in the fork, fill the fork and pump the damper rod to purge the air and fill them back up. This will draw new fresh fluid into them. You can also do a flush with the new fluid once too to get any remaining sediment out of them and then do a second refill.

Most folks ignore fork oil and don't change it often enough. Most manufactures tell you to change it about every 16K miles. I typically do mine once a year.

 

[SkooterG]

Most folks ignore fork oil and don't change it often enough. Most manufactures tell you to change it about every 16K miles. I typically do mine once a year.

Interesting that Yamaha has no service schedule whatsoever for fork oil replacement on the FJR. I wonder what the heck they were thinking.

 

[quicksilver]

Is everyone using 10 weight fork oil?

I put new 10W in, in August.

Even significantly tightening the compression and rebound, the front Avon is still squirmier than before on hard decel.

I now have new .95 kg/mm springs to put in.

Newer rear shock coming and a preload shim waiting for it..

Stick with 10 W?

Go thinner?

 

[evil_henchman]

Is everyone using 10 weight fork oil?I put new 10W in, in August.

Even significantly tightening the compression and rebound, the front Avon is still squirmier than before on hard decel.

I now have new .95 kg/mm springs to put in.

Newer rear shock coming and a preload shim waiting for it..

Stick with 10 W?

Go thinner?

Must I say it again? Ignore the "W" numbers when it comes to suspension oil. They're worse than useless. Read this.

 

[markjenn]

Interesting that Yamaha has no service schedule whatsoever for fork oil replacement on the FJR. I wonder what the heck they were thinking.

They were thinking that it probably isn't worth the trouble for most owners.

Changing it now and then is a good idea from a wear and corrosion standpoint, but I'm totally skeptical of folks who report that their fork performance is dramatically changed by simply replacing old oil with identical new oil. There is really no scientific reason for the oil to wear out or even to become very contaminated. The hydraulics of forks, while extremely sensitive to the design of the internals with respect to damping, makes very little demand on the damping oil.

- Mark

 

[Fred H.]

You might be surprised to see how hot your fork oil gets, and how dirty it is when you drain it out. Go for a ride and drain it and see for yourself how hot and dirty it is.

This stuff went in pink and in 12K miles it turned black.

The teflon on the bushings wear and so do the sliders, depositing metal into the oil. The oil also breaks down. It begins to get thinner in the early stages, and if not changed will then start to thicken and turn to an almost mud like composition. The change in viscosity alone is enough to affect damping qualities (both compression and rebound).

But don't take my word for it, go ask any suspension expert that rebuilds forks and shock for a living. Go talk to the folks at Traxxion or Works Performance or Ohlins or any other suspension expert and see what they tell you about changing the fork oil.

 

[markjenn]

You might be surprised to see how hot your fork oil gets, and how dirty it is when you drain it out. Go for a ride and drain it and see for yourself how hot and dirty it is.
This stuff went in pink and in 12K miles it turned black.

The teflon on the bushings wear and so do the sliders, depositing metal into the oil. The oil also breaks down. It begins to get thinner in the early stages, and if not changed will then start to thicken and turn to an almost mud like composition. The change in viscosity alone is enough to affect damping qualities (both compression and rebound).

But don't take my word for it, go ask any suspension expert that rebuilds forks and shock for a living. Go talk to the folks at Traxxion or Works Performance or Ohlins or any other suspension expert and see what they tell you about changing the fork oil.

Well suspension experts that "rebuild shocks and forks for a living" are certainly going to be on the side of doing more maintenance. Jiffy Lube still recommends 3K car oil changes when the the mfgs are saying 10K. It's not because JF knows more about oil.

Just like in your crancase, changes in oil color are not a good indicator of oil wear/tear. It's just the oil doing it's job and holding stuff in suspension. And I've never seen fork oil with 12K miles look terribly dirty unless there is a seal problem.

I'd like to see someone do some before/after viscosity tests on fork oil before I believe there is any significant viscosity breakdown.

Look, I agree, it's a good idea to change your fork oil now and then, but I see ridiculous suggestions for over-maintenance on this and other forums all the time. On a street bike, doing it every 10-15K or every couple years would be my recommendation and this is probably overkill. And as someone else point out, Yamaha does't bother to make any recommendation - as far as they are concerned, you can leave it in indefinitely.

- Mark

 

[Warchild]

But don't take my word for it, go ask any suspension expert that rebuilds forks and shock for a living. Go talk to the folks at Traxxion or Works Performance or Ohlins or any other suspension expert and see what they tell you about changing the fork oil.

Lord knows I don't always agree with FredH's pontifications, but on this issue, he is absolutely 100% correct.

It is definitely wise to flush/refill your fork oil on some periodic basis... what that interval should be is dependent on how you use your bike, your particular riding environment, and the amount of mileage you tend to garner over a particular time period. Unless your bike is a garage queen, I would suggest at least an annual fork oil change.... perhaps in the mid/late Spring, before the serious riding season gets underway.

Basing fork oil change intervals on viscosity properties alone is ill-advised. As FredH correctly observes, the teflon on the bushings do, in fact, wear over time, as do other internal components. Further, dusts seals will still allow a small amount of dirt to pass through, all of which contribute towards contamination of the fluid. Unlike engine oil, there is no filter to clean these small contaminates out of the fork oil. This alone suggests that regular changes are a good idea, if for no other reason that to remove these contaminates before they wedge somewhere and do Bad Things to fork internals.

Here's a photo of some Silkolene Pro RSF 2.5wt fork oil that went in to my Blackbird's forks a splendid honey-gold color. This is what it looked like approximately 3 months/10,000 miles later:

If you look hard enough at this photo below, you can almost see the suspended particulate matter.... THIS is why it's a good reason to periodically change fork fluid!

 

[quicksilver]

Must I say it again? Ignore the "W" numbers when it comes to suspension oil. They're worse than useless. Read this.

OK.......so that didn't get me any closer to selecting an applicable product, interesting as it was.

The FJRTech guide writeup called out Belray 10W which = 33.0 cSt@40C.

Does this imply any fork oil cSt@40C = 30 - 36 should have similar results?

I used Spectro 10W which has almost identical cSt@40C = 32.80, yet results were unsatifactory for me.

Low speed damping allows the front end to track the weaving Avon trend pattern far worse than the old OE oil did.

Does this mean I need thicker oil which would be less hyper responsive on decel?

Like Silkolene Pro RSF (7.5W) = 37.0 sTt@40C?

I assume the OE oil was Yamaha G10? cSt@40C = 33.2 (when new).

Can anyone confirm this?

 

[evil_henchman]

The FJRTech guide writeup called out Belray 10W which = 33.0 cSt@40C.
Does this imply any fork oil cSt@40C = 30 - 36 should have similar results?

I used Spectro 10W which has almost identical cSt@40C = 32.80, yet results were unsatifactory for me.

Low speed damping allows the front end to track the weaving Avon trend pattern far worse than the old OE oil did.

Does this mean I need thicker oil which would be less hyper responsive on decel?

Like Silkolene Pro RSF (7.5W) = 37.0 sTt@40C?

I assume the OE oil was Yamaha G10? cSt@40C = 33.2 (when new).

Can anyone confirm this?

The OEM oil is Yamaha 01 Fork Oil (15.6 cSt @ 40C). If it worked better as you claim I'd go that direction.