Fork oil viscosity, experiences?

[~TABASCO~]

That's interesting. Any chance you can show me what the jam nut looks like?
I seem to have some slight differences in clicks, don't remember exactly but I believe that both on compression and rebound that one had 9 and the other 10 or something like that.

#16....... jam nut

 

[~TABASCO~]

Next time in my forks I will have to pay close attention to that! thanks. I need to service them soon!

If you put it together and you dont have equal clicks.... and the total amount of clicks, the position of the rebound screw and the nut are not installed correctly.....

 

[kjetil4455]

Compression is on bottom and doesn't have anything to do with the 'nut'....... the rebound is on top and L & R should be the same (on stock forks) I thought It was like 13-14-16 clicks... (I would have to check in the book)

I think it's 10 on fork and 30 on the monoshock but I might be mistaken, don't remember.
Ok, only nut then; I'llreview that. Thanks man

Thanks for the illustration, that's very helpful!

 

[SkunkWorks]

Could it be that my yamaha tech poured too much oil in there?
Manual says 505mL per side, as far as I know, so we separated one liter equally into 500mL on each side. We didn't measure, only followed the volume specs.

However, it has been my understanding - and correct me if I am wrong - that oil volume has more to do with total travel, whereas oil viscosity determines the ease or difficulty of travel (ie. the amount of friction generated as the oil passes through the valving). How would reducing oil level increase traveling speed / ease of the fork? Thanks

I've done XT1200 Forks three separate times, and each time I have measured the fluid height exactly as stated in the shop-manual.
If you do it right and bleed all the air out the way you're supposed to, and measure the level like you are supposed to, you should end up with some fluid leftover out of a 1-liter bottle.
If your tech-person just divided it up equally and dumped half in each fork then it is over-filled slightly...................enough to really matter? Maybe not?
This is my experience using a 1-liter bottle to fill both forks.

 

[kjetil4455]

I've done XT1200 Forks three separate times, and each time I have measured the fluid height exactly as stated in the shop-manual.
If you do it right and bleed all the air out the way you're supposed to, and measure the level like you are supposed to, you should end up with some fluid leftover out of a 1-liter bottle.
If your tech-person just divided it up equally and dumped half in each fork then it is over-filled slightly...................enough to really matter? Maybe not?
This is my experience using a 1-liter bottle to fill both forks.

Thanks, I am waiting for the levle measurement tool to arrive (yamaha here doesn't have one!), and I'll go there and get this sorted. Gotta recheck everything; it's clearly not right.

 

[nd4spdbh]

Thanks, I am waiting for the levle measurement tool to arrive (yamaha here doesn't have one!), and I'll go there and get this sorted. Gotta recheck everything; it's clearly not right.

Use a long zip tie as a dipstick for your measuring tool. Dip it down into the fork all the way till the head of the zip tie rests on the fork, then pull out and measure with a ruler your fluid level. No need for fancy tools.

 

[kjetil4455]

Use a long zip tie as a dipstick for your measuring tool. Dip it down into the fork all the way till the head of the zip tie rests on the fork, then pull out and measure with a ruler your fluid level. No need for fancy tools.

Thanks brother

 

[kjetil4455]

OK, so an update.
One fork had a whopping 80mL excess, and the other 50 to 60. I also found that one of the spring guides were inverted. The high oil levels are likely the cause of the felt hydrolocking when hitting an object very hard, but does not explain the harshness of the fork at low speed nor by minor bumps. We fixed the excess oil (leveled air depth to 150mm with the spring taken out and fork fully compressed) and also calibrated the screw height that tabasco was talking about (it should be 12mm from screw top to axel top). Re-used my 5W viscosity fork oil as it has 3 months of use.

Long story short, the fork is still very rigid even with stock springs.
I am getting increasingly suspicious that 0W is the original oil viscosity, despite reading numerous claims of otherwise. Or maybe the fork oil I have received was simply poorly calibrated and much thicker than it should be (I have read the posted earlier that viscosity is a complicated topic, but nonetheless, reducing from 15W to 5W should show a marked difference and it has not).
Or, my fork is simply fucked. But that would be strange, considering no crash or any similar problems.

Sag is perfect at 6.2cm. We set the torqued the triple clamp to ensure that there would not be stiction (20Nm inferior and 26Nm upper clamp).

I tested the calibration screws (clickers) when I had the fork legs separated, by hand, screwing them all the way in and all the way out, and they cleary work.
So, again, the only thing I am left with is the choice to reduce viscosity. The tech at yamaha keeps saying "I think it's 0W" but he's not sure, and the manual obviously does not state the generic viscosity, just the compatible yamaha product. I keep hearing everyone on this forum saying 5W -- so I really don't know what to think anymore.

What am I missing?

Thanks guys

 

[cyclemike4]

OK, so an update.
One fork had a whopping 80mL excess, and the other 50 to 60. I also found that one of the spring guides were inverted. The high oil levels are likely the cause of the felt hydrolocking when hitting an object very hard, but does not explain the harshness of the fork at low speed nor by minor bumps. We fixed the excess oil (leveled air depth to 150mm with the spring taken out and fork fully compressed) and also calibrated the screw height that tabasco was talking about (it should be 12mm from screw top to axel top). Re-used my 5W viscosity fork oil as it has 3 months of use.

Long story short, the fork is still very rigid even with stock springs.
I am getting increasingly suspicious that 0W is the original oil viscosity, despite reading numerous claims of otherwise. Or maybe the fork oil I have received was simply poorly calibrated and much thicker than it should be (I have read the posted earlier that viscosity is a complicated topic, but nonetheless, reducing from 15W to 5W should show a marked difference and it has not).
Or, my fork is simply fucked. But that would be strange, considering no crash or any similar problems.

Sag is perfect at 6.2cm. We set the torqued the triple clamp to ensure that there would not be stiction (20Nm inferior and 26Nm upper clamp).

I tested the calibration screws (clickers) when I had the fork legs separated, by hand, screwing them all the way in and all the way out, and they cleary work.
So, again, the only thing I am left with is the choice to reduce viscosity. The tech at yamaha keeps saying "I think it's 0W" but he's not sure, and the manual obviously does not state the generic viscosity, just the compatible yamaha product. I keep hearing everyone on this forum saying 5W -- so I really don't know what to think anymore.

What am I missing?

Thanks guys

Ok here is my very uncontrolled experiment on fork oil wieghts. I have maxima 5w and i have PJ1 01w oils on hand. I filled a syringe to the top and timed the flow till empty. While the 5w to the eye looks very thin and as thin as the 01w but with a stop watch it takes consistantly just over 3 seconds longer for it to drain out. That sounds like a big jump in viscosity to me. Piddling in the shop today. Thought i would test it.

 

[kjetil4455]

Ok here is my very uncontrolled experiment on fork oil wieghts. I have maxima 5w and i have PJ1 01w oils on hand. I filled a syringe to the top and timed the flow till empty. While the 5w to the eye looks very thin and as thin as the 01w but with a stop watch it takes consistantly just over 3 seconds longer for it to drain out. That sounds like a big jump in viscosity to me. Piddling in the shop today. Thought i would test it.

3 times longer; I knew it. Thanks, this is very helpful. Gotta open this crapup ONE more time, then... And finally finis with this.

 

[Cycledude]

Fork oil, I quit buying fork oil many years ago and switched to synthetic automotive transmission fluid .seems to work about the same and much cheaper.

 

[kjetil4455]

Fork oil, I quit buying fork oil many years ago and switched to synthetic automotive transmission fluid .seems to work about the same and much cheaper.

I’ve read about it, mostly negative as such. But seeing as there’s no compatible oil here in my area I might try the engine oil meanwhile …

 

[OldRider]

Fork oil, I quit buying fork oil many years ago and switched to synthetic automotive transmission fluid .seems to work about the same and much cheaper.

There was a time many years ago when there was no such thing as fork oil and most service manuals called for ATF in forks. Back then forks were pretty simple, but todays forks are a lot more complicated and it's probably best to use modern fork fluid with the needed additives for the best performance.

 

[Cycledude]

I’ve read about it, mostly negative as such. But seeing as there’s no compatible oil here in my area I might try the engine oil meanwhile …

ATF fluid and fork oil are very similar, I wouldn’t recommend trying engine oil In fact I wouldn’t recommend using anything but what the manufacturer recommends, but ATF fluid is what I have been using for many years and it’s never caused me any trouble so I’m going to continue using it.

 

[cyclemike4]

Waaaaaaaaaaay back a few years ago when I was a kid we would use automatic transmission fluid stole from dad or tractor hydraulic fluid stole from my grand dad for our forks. Of course even finding any kind of motorcycle part was almost impossible much less finding the right fluids for one. We never had much luck with the ATF. It seemed to make the seals leak bad and the front of the bikes felt very bouncy and loose. Of course all our bikes were beat to death and already 15 years old before we got them. May have been fine with good forks. All I knew that fix got us boys another weekend ripping sod!

 

[kjetil4455]

FYI my friends; I found this excellent information. Turns out that the original 01 oil has a viscosity rating of 18, and this is extremely variable from brand to brand (this was already pointed out by one of you here). Anyway, this guy from another forum did us all a favor and listed the brands that have similar viscosity ratings. For me, that Motul 5W oil was the most readily available.

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

 

[kjetil4455]

Hopefully a final update: I decided to consult with Dave Moss and he said that the Fork oil 01 is 15.6 Centistokes -- I also found the same information on other tables online.

In other words, compatible products would be

Yamaha fork oil 01, 15,6 cSt
Motul fork oil 2,5W very light 15 cSt
Red Line Light Weight Suspension Fluid 16 cSt
SUZUKI L01 15.5 cSt
KAWASAKI KHL-15-10 15.3 cSt
SHOWA SS-05 15.7 cSt
Castrol Fork Oil 5 Fork & Shock Oil 15 cSt
Ohlins 1311-02 Front Fork Fluid #5 Light 15 cSt
Ohlins 1311 25mm cart kit Front Fork Fluid #4 15 cSt
Motul Shock Oil Shock Oil 16.1 cSt
Maxima Fork Oil 5wt Fork Oil 15.9 cSt
Motorex Racing Fork Oil 2.5 Fork Oil 15.2 cSt
5W Shell Advance Fork Oil 15 cSt
5W Putoline Light Fork 15 cSt
5W Liqui Moly Shock Oil 15,3 cSt
3W IPONE Fork Fluid 3 Racing 15,5 cSt
5W Fox Racing Oil 15,8 cSt
5W KYB 01M 15,85 cSt
5W KYB KHL15-11 15,9 cSt
5W Valvoline SynFork 16 cSt
5W RockShox 16,1 cSt

Hopefully this will help someone to avoid wasting as much time as money as I have on this bullshit

 

[kjetil4455]

Fork oil level is measured with the fork fully compressed and without the spring. I use kyb 01 fork oil and .95 constant rate springs from Sonic.

Garry, what's your weight and how much sag do you get with these springs? I'd like a linear spring that gives me 6cm (perfect) of sag with zero preload