Fork Oil, Snake Oil, or Just Another Oil Thread

[veriest1]

I've put it off long enough. I need to put new seals on my 07 FJR forks. I think they just deteriorated from age as the bike only has about 20k miles on it. Therefore I don't think I'll need to completely rebuild the forks.

However, I do want to put fresh oil in while I'm at it. I was planning to use BelRay 10w but in researching it for this bike I came across this post on another forum and it kind of scrambled my brain on what fork oil to run since I've always been told and assumed 10w was thicker than 5w etc. It just makes sense but it doesn't seem like that's necessarily what we need to be going off of.

2009 fork oil weight

www.fjrowners.com

So I cruised over to Motuls website and found their Technical Data Sheets for their 5w, 7.5w, and 10w oils.

First the 5w:

Next is the 7.5w (I know it says 10w for some reason but this is from their .pdf file for the Light/Medium 7.5w oil):

And lastly 10w:

I found all this very interesting since we can easily have ambient temperatures in the 104F range but I really don't know how hot forks get under spirited riding conditions. I'm currently considering going for the 7.5w oil just because of how hot it gets here and to stiffen the front end up a bit since I'm a solid 220 pounds with gear on. What are your thoughts?

 

[DFW_Warrior]

Forget about the oil, aren't the FJR's the ones with the weird double fork bushing thing going on? That is much more to worry about than the fork oil.

 

[veriest1]

Forget about the oil, aren't the FJR's the ones with the weird double fork bushing thing going on? That is much more to worry about than the fork oil.

That's a good question. I've looked at pictures of the internals and they're different than anything I've done in the past but I didn't realize they could be an issue. It looks like the bushings can get messed up by taking the forks apart to change the seals.

 

[dukey33]

I would say go thicker only if you feel like you want more damping from the forks. If you're content with how they respond, just use the factory spec weight.
Keep in mind what the back shock is doing.
If the bike is pogo-ing on the front forks because the rear shock is dialed-up, some stiffening will help match it. If there is a significant difference, more spring preload or heavier springs may be needed in the forks.

 

[FE_Rex]

http://mahonkin.com/~milktree/motorcycle/fork-oil.html

 

[veriest1]

I would say go thicker only if you feel like you want more damping from the forks. If you're content with how they respond, just use the factory spec weight.
Keep in mind what the back shock is doing.
If the bike is pogo-ing on the front forks because the rear shock is dialed-up, some stiffening will help match it. If there is a significant difference, more spring preload or heavier springs may be needed in the forks.

It's a little soft. I'm at the edge of the useable adjustment range for the stock suspension at 220 pounds geared up. I need to do something about the rear shock eventually as it's atrocious.

My biggest gripe with the suspension at both ends of the bike is the high-speed compression. It's really chattery on rough pavement.

http://mahonkin.com/~milktree/motorcycle/fork-oil.html

That looks like a great resource. Thank you!

 

[DFW_Warrior]

That's a good question. I've looked at pictures of the internals and they're different than anything I've done in the past but I didn't realize they could be an issue. It looks like the bushings can get messed up by taking the forks apart to change the seals.

Yeah, it is kind of a thing for sure. Lots of heat, but not aluminum melty heat is usually the answer. That and luck....

 

[fossil]

You may surprised what the dust seals allow to pass on into the oil seals. One of mine developed a leak (07 FJR) that was resolved by cleaning the grit out with a Seal Saver. An easier to manipulate model was more effective and successful used on a VTX and Yamaha Majesty.

 

[veriest1]

You may surprised what the dust seals allow to pass on into the oil seals. One of mine developed a leak (07 FJR) that was resolved by cleaning the grit out with a Seal Saver. An easier to manipulate model was more effective and successful used on a VTX and Yamaha Majesty.

View attachment 350311

Yeah, I’ve got a little cleaner thingy and it worked last year but one has cracked now and it’s spewing oil all over the place upon compression so it’s going to need all the seals done.

I’ve got new seals and bushings on the way but I haven’t ordered any oil yet.

 

[OldTLSDoug]

Larry, I use the maxima stuff and the motorex stuff mostly these days in the stock weight. If you don't like the damping you might consider the Race Tech Gold Valve alternative and different springs. Don't know if the FJR shock is rebuildable, but we could probably figure it out. I have the equipment to vacuum fill a wp shock, surely we could figure it out. Might even be a Gold valve for the rear as well. Your choppiness could also be poor rebound performance, not only compressing too fast, but returning too fast as well. Be careful of bike forums as they auger in on things that may or may not help, but seek several opinions and try a direction. Forks and oil are simple and relatively inexpensive to modify/maintain, so it is worth playing with.

 

[mr72]

It's a little soft. I'm at the edge of the useable adjustment range for the stock suspension at 220 pounds geared up. I need to do something about the rear shock eventually as it's atrocious.

I think this is related to the other issue. The problem is that you are not changing the spring RATE by adjusting the "preload". Preload is really just a ride-height adjustment, more or less. If you increase the weight temporarily, like riding with a pillion, then increasing the ride height can prevent reduce bottoming, but it's not going to actually make the suspension any stiffer if you have single-rate springs.

If you put in progressive springs then the preload actually will increase spring rate and make the forks stiffer by putting the lighter weight portion of the spring into coil bind earlier in the travel.

My biggest gripe with the suspension at both ends of the bike is the high-speed compression. It's really chattery on rough pavement.

This is a spring rate problem first (IMHO) and then a corresponding damping problem. You can't fix it with damping alone. The easiest way to fix the rear is with a stiffer spring and a shock with an adjustable damper, both compression and rebound, so you can dial it in to match the road surfaces you experience. Remember damping in a conventional shock absorber is like a low-pass filter. If you want the ride less "chattery" over rough pavement, you actually need lighter damping, so the suspension can move both up and down to follow the road without the rest of the chassis moving with it. As you might expect then, this is speed dependent. Lighter damping will likely allow the suspension to oscillate with lower-speed bumps, like smooth road irregularities on normal higher speed roads. It can be very tricky to get it to where it will ride smooth (wheel moves quickly up and down) over fast/frequent bumps (which we would oddly call "low speed bumps", just because we slow down to ride over them) and also doesn't oscillate dangerously when riding on smooth roads at higher speeds. You have to compromise.

Why this is tricky is because our perception is that an overdamped fork or shock feels "stiff", but that's because it cannot move over "fast" bumps, that is hard-edge bumps like roadway separations or pavement steps or even these small potholes like litter all of our central TX county roads. But the actual spring rate is not stiffer. The springs are not unable to compress over these bumps, just the damper won't move. Then on lower rate bumps, say, speed hump, or a dip in the road at the bottom of a hill when it transitions to uphill, it may still bottom out. You need a stiffer spring. But a stiffer spring requires more rebound damping because it applies more force on rebound, making it rebound faster.

So to sum up, I think if you are 220 lb you definitely need stiffer springs on both ends. If you want to be able to dial in the fork stiffness with the preload then you might get away with a progressive spring in the front, but otherwise I'd hit up Sonic Springs and just get springs for your weight and bike from their recommendation. Then you need to up the oil viscosity by the same quotient as what you did to change the spring rate. So if you have 60 kg/mm springs stock and you wind up with 85 kg/mm, and you have stock ~20 viscosity (like Bel-Ray 5wt), then 85/60 = 1.42, 20*1.42 = ~28, so pick a fork oil with viscosity around 28 (Castrol 5wt, Bel-Ray 7wt..). For the rear, I not nearly as easy to DIY.

That looks like a great resource. Thank you!

That is a great resource. I always use Maxima fork oil but I did buy some Bel-Ray that I put in my GS fork when I changed to the 80kg/mm springs and I notice it's 50% higher viscosity in the 7wt than the Maxima I normally use. Works fine for that bike with those springs, but it's not surprising now that I noticed a night and day difference in damping. I need to rebuild the Scrambler fork so I'll be looking closely at this, probably go back to the Maxima I know intuitively.

Full disclosure, I have loads of experience fine tuning suspension on mountain bikes and less on motorcycles. Principles are the same but there are considerations on mountain bikes that don't apply on a motorcycle, mostly related to pedaling and the fact that 80-90% of the weight is the rider and not the vehicle.

 

[Cagiva 549]

If you have ever had a fork oil leak on a bike with store bought fork oil , you may notice it takes a steam cleaner to get it off . The nastiest gooyest gunk I have ever encountered with no good quality’s about it . Nothing but atf in any fork I ever rebuilt and you can tune your ride by what viscosity oil is used and when you drain it 5 years later the bottom of your fork isn’t full of mud .

 

[Gravel Guy]

Second the ATF.

 

[RTL]

No ATF for my suspension. ATF is not formulated for use as suspension oil.

 

[Gravel Guy]

No ATF for my suspension. ATF is not formulated for use as suspension oil.

Nope, it's formulated for much more grueling conditions that most fork oils will ever see. It's only worked successfully for 80K in my KLR.....

 

[DFW_Warrior]

Nope, it's formulated for much more grueling conditions that most fork oils will ever see. It's only worked successfully for 80K in my KLR.....

Yeah, but that is a KLR!!!! You could run bacon grease as fork oil (and probably engine oil) and that thing wouldn't know the difference!

 

[veriest1]

I think you guys are probably on to it with the spring rate thing.

I know with three way adjustable shocks I’ve had good results being able to tune high and low speed compression independently (on the GSA and 500X) but that was also with proper spring rates. Forks are more of a mystery to me as the only ones I’ve done I’ve had good resources where I could just plug and play their valve, spring, and oil solutions and they were more than adequate for my needs.

Larry, I use the maxima stuff and the motorex stuff mostly these days in the stock weight. If you don't like the damping you might consider the Race Tech Gold Valve alternative and different springs. Don't know if the FJR shock is rebuildable, but we could probably figure it out. I have the equipment to vacuum fill a wp shock, surely we could figure it out. Might even be a Gold valve for the rear as well. Your choppiness could also be poor rebound performance, not only compressing too fast, but returning too fast as well. Be careful of bike forums as they auger in on things that may or may not help, but seek several opinions and try a direction. Forks and oil are simple and relatively inexpensive to modify/maintain, so it is worth playing with.

View attachment 350315

The problem with the factory shock is its preload isn’t adjustable except via that goofy switch thing so setting sag is basically impossible. It has a very basic compression adjustment on the bottom and no rebound adjustment.

On the other end the forks have preload, compression and rebound but the compression adjustment impacts both the high and low speed settings so it’s always a compromise in my experience. But some of that could be the spring rate and having to account for them being soft.

The settings I have right now are the best I’ve had with it but it still doesn’t feel “planted” mid corner. The problem is going harder makes it to “skittish” and softer makes it “wallow.”

I haven’t changed my suspension setting since last October because I don’t think they’re going to get much better than this for my weight.

 

[Cagiva 549]

Atf is also the best lubricant in the world for seals .

 

[Irishcoffee]

Larry, I use the maxima stuff and the motorex stuff mostly these days in the stock weight. If you don't like the damping you might consider the Race Tech Gold Valve alternative and different springs. Don't know if the FJR shock is rebuildable, but we could probably figure it out. I have the equipment to vacuum fill a wp shock, surely we could figure it out. Might even be a Gold valve for the rear as well. Your choppiness could also be poor rebound performance, not only compressing too fast, but returning too fast as well. Be careful of bike forums as they auger in on things that may or may not help, but seek several opinions and try a direction. Forks and oil are simple and relatively inexpensive to modify/maintain, so it is worth playing with.

View attachment 350315

 

[veriest1]

Any recommendations for a supplier for a rear shock for the FJR? Ive looked at some over the last couple of years but nothing really stood out.

I think I’ll go ahead and do both ends at the same time.

Edit: I’m currently leaning towards the Penske or Ohlins. Both seem to have some pros and cons.

 

[Gravel Guy]

Any recommendations for a supplier for a rear shock for the FJR? Ive looked at some over the last couple of years but nothing really stood out.

I think I’ll go ahead and do both ends at the same time.

Edit: I’m currently leaning towards the Penske or Ohlins. Both seem to have some pros and cons.

@veriest1 have you called CuznBob? He’s got more suspension options than these. . If you need his number I’ll PM you..