Fork Oil

[Skid Mark]

Hi Gents,
I have to change a fork seal on one leg, I can't remember the brand of Oil I used. Reading a tread here some time ago, there seems to be quite a difference between different brands. Should I change out completely or will a top up of correct grade, but different oil do?

[Al]

Hi Phil, SAE is a range rather than an actual number. 15 is probably from 12.5 to 17.5 for example. Not all producers use SAE, or use it the same way so its a bit of a lottery. Cst is the correct way to assess fork oil and you wont get that on the bottle. Safest to change it all since you need to buy a bottle anyway. Or change the same amount in each leg with the top-up.
Its probably more important to get the level right and of course the superseeded fork oil seals which KHI changed on the 38mm forks because of endless failures of the original type of seals!!
http://mahonkin.com/~milktree/motorcycles/fork-oil.html

AL

[zed1015]

I always do both seals even if only one is leaking as you can bet the other won't be far behind but if only changing one i would still put fresh oil in both legs the ensure the damping remains the same.

[Skid Mark]

Hi Phil, SAE is a range rather than an actual number. 15 is probably from 12.5 to 17.5 for example. Not all producers use SAE, or use it the same way so its a bit of a lottery. Cst is the correct way to assess fork oil and you wont get that on the bottle. Safest to change it all since you need to buy a bottle anyway. Or change the same amount in each leg with the top-up.
Its probably more important to get the level right and of course the superseeded fork oil seals which KHI changed on the 38mm forks because of endless failures of the original type of seals!!
http://mahonkin.com/~milktree/motorcycles/fork-oil.html

AL

Thanks Al, Sound advice as always!
P

[Skid Mark]

I always do both seals even if only one is leaking as you can bet the other won't be far behind but if only changing one i would still put fresh oil in both legs the ensure the damping remains the same.

Thanks Rob, I agree with you on changing both, but the issue is damage rather than ware. I was feeling lazy, but I think I need to do both to be sure.