Help SSS Fork oil Change 2018 YZ250 2T

[MikeT]

Ok, I just got this bike 2016 YZ250 2T and it has forks and a shock off a 2018. I know it is probably exactly the same but incase there is a difference I am noting it. Yesterday I changed the fork springs and it is much more involved than my old 2000 forks.
I poured out the oil and when I got the inner "strut" thing out, I noticed that it has oil in there also but I was told that I did not need to change that.

My question is this;
1. Do I need to change this "internal" oil, how and how often?
2. If I put in a different weight oil on the outer oil, say 10w instead of 5w, does it have any effect on the system or does all the dampening come from the inner strut/oil??

 

[Pete Payne]

Hello!
Both of the fork oils should be changed in the 30-40 hour mark.
Use the same oil in both cambers. Even though the inner chamber is sealed. the outer oil will get pushed into it via the bottoming cone in the bottom of the fork when the fork is bottomed. The pressure in the cone becomes greater than the bottom chamber seal can hold and the outer oil will get squeezed into the inner chamber.
Don't worry though , it will not over fill the inner chamber doing this . They have it set up so it will self purge out of the top of the ICS chamber.

 

[MikeT]

Thanks, Pete. The forks only have about 6 hours on them so I am told. I went to stiffer springs so I put 10W oil in them. I had no idea these forks had an inner and outer anything. I am guessing that the 10 will simply mix with the inner and eventually become a 7.5 or so based on the volumes.

Is this a correct assumption?

 

[MikeT]

I put the 10W in the outer chamber only

 

[Pete Payne]

Yes it will mix at some point .