2009 fork oil weight - Page 2 - Yamaha FJR Forum : Yamaha FJR Owners Forums
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post #11 of 30 (permalink) Old 11-09-2020, 02:15 PM
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From the linked article:
"SAE Oil Weight DO NOT GO BY LABLED OIL WEIGHT! Not only is this a poor way to decide which oil to use, but each manufacturer seems to be on a different scale. For example Maxima RSF 7wt is actually lighter than Spectro 5wt and Silkolene Pro RSF 7.5wt is actually heavier than Showa SS-8 10wt. This is not a judgment about the quality of these oils, just that the 'weight' label leads to a lot of trouble when trying to tune with suspension oils.
These problems can be seem graphically by comparing several systems to each other. Viscosity comparison chart Courtesy of Shell Oil.
Suspension oil is labeled by weight because consumers are used to thinking of oil (ie. motor oil & gear oil) in these terms. The SAE weight system has a very broad and vague viscosity range and does not even cover the viscosity range that most quality motorcycle suspension systems require. Another point of confusion is that motor oils and gear oils are rated for viscosity on the SAE scale at different temperatures, leading to similar viscosity oils having very different ratings. SAE J300 is used to define engine oils, while SAE J306 is used to define drive line (gear) and chassis lubricants."


I think this is the key point. Fork oil is worse than engine oil, gear oil, and ATF in that respect.If you want to tinker with your fork oil, you are better off finding an easily available, reputable brand and sticking with it.

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post #12 of 30 (permalink) Old 11-09-2020, 04:03 PM
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Just an honest question/observation.

For the kind of riding we do, does fork oil really make any difference?

I have use Harley Davidson, Bel-Ray, and Honda Fluid brand, and quite frankly, have not really noticed a marked improvement or difference.

I mean maybe? if I am tearing up the Circuit of Americas, or SECA on my 600RR, but on the FJR, I just don't know if it makes a difference.

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post #13 of 30 (permalink) Old 11-09-2020, 05:14 PM
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Originally Posted by skippy344! View Post
Just an honest question/observation.

For the kind of riding we do, does fork oil really make any difference?

I have use Harley Davidson, Bel-Ray, and Honda Fluid brand, and quite frankly, have not really noticed a marked improvement or difference.

I mean maybe? if I am tearing up the Circuit of Americas, or SECA on my 600RR, but on the FJR, I just don't know if it makes a difference.

Convince me!
When I replaced the fork seals on my 2006 gen2 I followed the advice in raesewell's post no 4 in this thread to get a handle on the correct viscosity fork oil to use. Local Yamaha dealer was no help just kept quoting part numbers - Didn't stock yamaha fork oil - special order only with a special price with a lot of zeros in it.

Riding after the fork rebuild has transformed the front end feel so I'm convinced that using the correct weight of oil can matter - how much you think it matters is individual choice!
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post #14 of 30 (permalink) Old 11-09-2020, 05:42 PM
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Originally Posted by raesewell View Post
This is an article I wrote a few years ago, oil weight has nothing to do with viscosity and it's viscosity that matters.

Before I started researching fork oil I didn't know much about it other than it was oily.
So I suppose you could say I knew fork oil about fork oil.

The searching started when I took my first ride after fitting my newly sealed forks.
They were stiffer than a stiff thing on a stiff day. In other word they were ,king stiff.
I had already purchased the oil before I sent them off so Ernie put it what I had sent him.

The manufacturers W numbers bear no resemblance to the viscosity.
The Yamaha manual recommends Yamaha Suspension Oil M1 or Ohlins R&T43.
Both of which seem pretty scarce in the uk. A US site tell me that Yamaha M1 is a zero weight oil but no viscosity figures. The Ohlins site however was more helpful giving a viscosity of 19 mm2 Centistokes @ 40 C. So I had a reference point to aim for.

I contacted Opie Oils for some advice and Tim (very helpful) set about finding me some suitable oil.
His first recommendation was for any 5W oil until I pointed out that it was the viscosity that was the critical factor as the 5, 7.5, 10W etc bore no resemblance to the viscosity. Telling him my aim was a viscosity of 19. He came back again with a recommendation for Motul Light 5W Factory Line Motorcycle Fork Oil which has a viscosity of 18, so close enough for me. I then set about finding others that were in the same range so I had a choice.
Fork Oil recommendations for the Yamaha FJR 1300A
Centistokes @ 40C
Millers Suspension Oil 2.5 NT 17.2
Motul Factory Line 5W Light (Synth) 18
Motul Expert 5W Light (Semi Synth) 18
Red Line Light Weight Suspension Fluid 16
Silkolene 02 17.94
Yamaha M1 18.7
Yamaha 01 15.3

So as you can see from the figures above the W number bears no resemblance to the viscosity.
The oil I supplied to Ernie turned out to have a viscosity of 47.4, no wonder it was bloody stiff.
The right oil is on its way from Ernie. I will use Opie next time I need fork oil, Tim, you are a top man.
Good info to have for the uninitiated forkers out there.
What was it that you first bought and had your fork guy put in your forks that has a viscosity of 47.5? That seems too far off on your first attempt not to tell what it was. This is a must know for the uninitiated FJR fork tuners fork oil notebook.
I used PJ-1 5wt in my first Gen. So far nothing out of the ordinary to report. Seems like it's right in the ballpark.

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post #15 of 30 (permalink) Old 11-10-2020, 05:50 PM
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Originally Posted by RaYzerman View Post
...but take a look at the 100C value as well.]
I wanted to take a moment and highlight this comment. A lot of the oils I see are available in the @40C viscosity, but there doesn't appear to be a correlation with the @40C and @100C values.

Just me being me, if the Yam01 is testing 15.5 @40C and 3.45 at @100C I would think the engineers considered that. Also me being me, I'm a bit heftier than most and might choose to go just slightly thicker. I can find a 18 to 19 @40C.

I was originally going to order up some synthetic Bel-Ray HVI 5W (25% increase to 19.5 @40C) but the high end is 6.66 @100C is way up from the calculated 25% increase to the 4.3 I would be looking for.

Here's the question: Wouldn't I also want to advance by the same percentage @100C?

If I increase spring rate from 0.8 to 1.1, a 25% jump, would I also want to mimic that with the fork oil viscosity?

Motul Facotry Line Very Light with 15 @40C and 3.5 @100C looks good for factory spec replacement.
Showa SS-7 with 16.6 @40C and 3.77 @100C is about 7% to 8% difference.
Motul Facotry Line Light with 18 @40C and 4 @100C seems about a 15% difference.
ELF Moto Fork Oil Syn 2.5 the same with 18 and 4.

Is my thinking correct on this?

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Last edited by Dale I; 11-10-2020 at 05:57 PM.
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post #16 of 30 (permalink) Old 11-10-2020, 07:11 PM
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Hey guys- I know it can be confusing but don't allow yourself to get so caught up in the numbers game that you paralyze yourself. Pick one, try it out. It's not like we're building a nuclear reactor here. If you like what you've chosen then fine. If not then dump it out and try another. IMHO don't use some off-the-wall brand. Use a brand with a wide range of options so you can choose better the second time if needed.
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post #17 of 30 (permalink) Old 11-10-2020, 08:02 PM
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Originally Posted by rbentnail View Post
Hey guys- I know it can be confusing but don't allow yourself to get so caught up in the numbers game that you paralyze yourself.
If you're saying don't be too obsessive.... well.... I've proven it's too late for that...

It's the engineer in me. I don't know if viscosity is linear.

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post #18 of 30 (permalink) Old 11-10-2020, 09:07 PM
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Originally Posted by rbentnail View Post
Hey guys- I know it can be confusing but don't allow yourself to get so caught up in the numbers game that you paralyze yourself. Pick one, try it out. It's not like we're building a nuclear reactor here. If you like what you've chosen then fine. If not then dump it out and try another. IMHO don't use some off-the-wall brand. Use a brand with a wide range of options so you can choose better the second time if needed.
That's why I asked the OP to tell us what he thought was right the first time and found it to be 30 numbers off the mark, and unrideable.
I use PJ1 fork tuner oil, works great. I've been using it for 30 years, never had a problem with it matching up to whatever I use it in.
To the original poster: What oil did you first buy that did not work?

Dale I, I don't see how viscosity could be linear with all the different make ups of oils. In your case, I would think you are on track with the correct spring rate for your weight, but I would stay with the factory specs on the oil first. Then go up from there if it doesn't suit you. The correct spring rate makes a significant change in performance and feel. Unless of course you run your FJR around the track all day.

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post #19 of 30 (permalink) Old 11-10-2020, 10:47 PM
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If you're saying don't be too obsessive.... well.... I've proven it's too late for that...

It's the engineer in me. I don't know if viscosity is linear.
On a calendar a gazillion years ago I read this:

"Paralysis by analysis is noise pollution at its worst."

Linear? Whatcha gonna do if it's not, replace the fork fluid for each ride where the temperature has changed 8 or 10 degrees? Of course not. You're going to chuck the fluid in and ride with it over a wide range of temperatures. So why obsess over what the viscosity is at 1 specific temperature?
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post #20 of 30 (permalink) Old 11-11-2020, 01:54 AM
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Fork oil weight is a personal choice

After switching to Racetech springs during my fork overhaul, I consulted a Racetech technician in my city who advised me to stay with a 5W oil. As Amsoil suggests, look at the data sheets provided by oil manufacturers and try to stay consistent. Some say to use a heavier oil during hot riding seasons and a lighter oil in cold riding season. Also, don't ignore your fork adjustments, especially rebound adjustment. Oil weight affects these. As Dave Moss says, change your fork oil regularly... only then will will you get consistent information, because fork oil degrades just as much, if not more so than engine oil.
I most recently went with the Maxima 5W. I think I'll try that out for awhile and change the oil I use depending on A: how I like it, B: environmental conditions, and C: if I run out of adjustment on the fork.
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