fork oil weight

Hello I 'm a new07 WR450 owner, I have been trying to find out what weight the oil is for the forks? I know it is Yamaha S1 but even the people at a local Yamaha store here don't know if its 1, 3, 5 or what weight it is. I tried to do a search and like I said I'm new but have not had any luck with the stock S1 oil weight any insight would be greatly appreciated. Thank you

Hello I 'm a new07 WR450 owner, I have been trying to find out what weight the oil is for the forks? I know it is Yamaha S1 but even the people at a local Yamaha store here don't know if its 1, 3, 5 or what weight it is. I tried to do a search and like I said I'm new but have not had any luck with the stock S1 oil weight any insight would be greatly appreciated. Thank you

Use 5wt.

5wt is about what it works out to. Yamaha S1 is a really good oil, but doesn't last very long, really, especially not for the kind of money they want for it.

Thank you

its actually closer to 2.5 weight, with a reported viscosity of 15.6 centi-stokes, but 2.5w fork oil is very thin which is great for fade resistance but provides little in the way of lubrication - see chart below

As you can see, one make of 2.5 wt is not the same as another make of 2.5 - choose a brand and stick with it - I have had good results with Motul Factory Line Fork oil, but even there Factory line oil differs from their ordinary oil in terms of viscosity so beware

PJ1 Fork Tuner 2.5w is 26.1 centistokes yet Castrol Fork oil 10Wt is thinner at 15 centistokes, which is the same as most other 2.5W oils!

Go with 5W

You will soon find that the forks are somewhat lacking in performance, bring harsh over small roots, yet blowing through the stroke and bottoming out really easy

This is due to the unique (rubbish) design of base valve in the fork

Have a read of this - http://www.thumperta...50-fork-valves/

I also suffered from a lack of rebound damping in my forks of my 08 model - it needed 10W oil to get anything resembling some damping in the rebound which just made the slow speed compression problem worse

When I opened up my forks to put gold valves in, I found the nut loose on the rebound stack, inside the cartridge, which was just letting the shims lift and the oil flow by without providing any damping

You may also find the fork springs to be soft, depending upon your riding style and weight

They are quoted as being 0.46kg/mm, but mine actually measured 0.41kg/mm, which came as no surprise to my suspension shop - he said WR's are notorious for underrated springs in the forks as they come from Yamaha

I put in some proper 0.44kg/mm springs and it transformed the bike (along with the gold valves), but then went to 0.46kg as my riding speed improved and I was working the bike harder

The stronger 0.46kg/mm springs overwhelmed the the stock rebound damping, so I had to increase the rebound shim stack strength from 6 x 0.1 face shims to 1 x 0.2 & 2 x 0.1, which gave me just abit more damping on the min setting to what I had on the max setting previously

PVD-ISO-Viscosity-Data.gif

Edited by GuyGraham
You may also find the fork springs to be soft, depending upon your riding style and weight

They are quoted as being 0.46kg/mm, but mine actually measured 0.41kg/mm, which came as no surprise to my suspension shop - he said WR's are notorious for underrated springs in the forks as they come from Yamaha

I put in some proper 0.44kg/mm springs and it transformed the bike (along with the gold valves), but then went to 0.46kg as my riding speed improved and I was working the bike harder

The stronger 0.46kg/mm springs overwhelmed the the stock rebound damping, so I had to increase the rebound shim stack strength from 6 x 0.1 face shims to 1 x 0.2 & 2 x 0.1, which gave me just abit more damping on the min setting to what I had on the max setting previously

Thanks - GuyGraham - good advice on oil and spring rates for the strange suspension on the WR --- how can the YZ be so good and the WR so .... so-so.

completey different forks internally, fitted to the WR. compared to the YZ - the Base valve is very strange unique design not seen on any other forks

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