Highest Fork Oil Viscosity without Problems (in cSt@40C)

[3alfa3]

So, what would be highest Fork Oil Viscosity in cSt@40C for stock Forks on Z900 (European 2020 Model if that makes a difference).

Kawasaki specifies 15,3 cSt@40C, i use 16 cSt@40C currently (no noticeable difference). Would 19 cSt@40C be to thick and possibly cause hidrolock? I read somewhere on this Forum that Z900 cannot use too thick oil for that reason, but, where is the limit?

Btw, i use Motorex 4W fork oil, but would try to mix it with 5W in 50:50 ratio (that would give 19cSt@40C). Is that too thick or still appropriate?

What oil do you use without any problem so i can check Viscosity in cSt@40C if you don't know Viscosity Value?

Here is the Chart for mixing Motorex Fork Oils: http://www.motorexoil.com.au/wp-dev/wp-content/uploads/2017/01/MOTOREX-Fork-Oil-Viscosity-Mix.pdf


Tnx

[n_zoomz]

I changed my fork oil from stock to 7.5W a few months ago and have done over 3000 miles since. I hope that helps with your concerns, I'm not sure what 7.5W is in cst and I haven't heard of too thick fork oil being an issue aside from making them too stiff/slow.

[3alfa3]

Originally Posted by n_zoomz

I changed my fork oil from stock to 7.5W a few months ago and have done over 3000 miles since. I hope that helps with your concerns, I'm not sure what 7.5W is in cst and I haven't heard of too thick fork oil being an issue aside from making them too stiff/slow.

That's the point: fork oil is not standardised like motor oil, so "weight" in number is not that important fact.
However, if you can write what Oil did you use, that would help, i can probably find online what viscosity in cSt@40C is.


Btw, did you need to change rebound setting and if yes, by how many clicks?  (with thicker oil, rebound is slower). My Motorex 4W oil is too close in Viscosity to stock oil so no rebound adjustment was needed.

[n_zoomz]

Interesting, I used "MAXIMA RACING FORK FLUID 7W"

Yes, my preload adjustment was far less than it was on stock oil. On stock oil I was maxed out.

With the fork oil change I am very happy at 4 clicks from fully in (200 lbs with gear and backpack). I don't know the stock setting off the top of my head, I changed my rebound and preload from stock as soon as I got the bike.

[KellyL]

Originally Posted by 3alfa3

So, what would be highest Fork Oil Viscosity in cSt@40C for stock Forks on Z900 (European 2020 Model if that makes a difference).

Kawasaki specifies 15,3 cSt@40C, i use 16 cSt@40C currently (no noticeable difference). Would 19 cSt@40C be to thick and possibly cause hidrolock? I read somewhere on this Forum that Z900 cannot use too thick oil for that reason, but, where is the limit?

Btw, i use Motorex 4W fork oil, but would try to mix it with 5W in 50:50 ratio (that would give 19cSt@40C). Is that too thick or still appropriate?

What oil do you use without any problem so i can check Viscosity in cSt@40C if you don't know Viscosity Value?

Check out this thread here: https://www.z900forum.com/index.php/topic,1456.msg31249.html#msg31249

When I tried 36cst in the fork it helped with rebound, but compression became too harsh. 20-26cst seemed to be more suitable.

[3alfa3]

Thanks everyone

[Idefix333]

@KellyL, did you change the oil volume ?

Original is 99mm
Wilbers recomend with his spring, 130mm with 32cst visc.oil
Zupin recomend with k-tech spring (9,5N) 115mm with 18cst