YZ125E rear shock, replace oil

[oldyzman]

Gday all,
I have had great success getting a shock revalved etc for my cr 83, the same co did my shock from a 79 yz250 which was a poor result. I now have the shock out of my YZ125E. Is it possible to replace the oil in this sucker myself. If so:
Would i use a 15wt oil and how much or to shat level??
Do i really have to charge it with nitrogen
or should i just send it to the shock dudes
Brett

[Nathan S]

They're easy to do. After you do the first one, you'll save a stack of money DIY.

http://www.bmsc.com.au/forums/rallying-technical/17490-diy-bilstein-shock-rebuilding.html

Your old Yammie shock is 99% the same. The only real difference is that the gas valve is already in your shock - at the bottom/rear end, with the small phillips head screw covering it.
 
If you need to replace the seal head, then be very cafeful with the rebound adjuster - they're made from a particularly soft aluminum alloy (designed to expand when hot and compensate for the oil thinning out). To make it worse, a fair number have been screwed in so hard that they're jammed into their seat in the shaft. If you try to dislodge it by pushing it out from the seal head end, you will almost certainly f#$k it.

Finding the hypodermic needles is becoming very hard. Last time, I had to visit half a dozen chemists before I found one that had the needles. And had to deal with five chemists who were convinced that I was a junkie and needed a fit-kit... It seems that 99.999% of people who want needles are junkies or diabetics  - and they both use the all-in-one disposable needle and syringe.
Might be worth trying a vet.

[oldyzman]

Thanks for the heads up nathan, i reckon that the adj is stuck, how would you get it free... Would you recharge it with nitrogen...
Cheers Brett

[Nathan S]

Compressed air with a GOOD water trap will work 99.999% as well as nitrogen.
Basically, the water that's usually in compressed air will cause the gas pressure to vary fairly signficantly with temperature. It could also cause corrosion inside the shock, I guess.
If you keep the water out, then air will work fine (and its nearly 80% Nitrogen anyhow).

What's going to screw you up, is that you'll struggle to find a tool to get your gas of choice into the shock via the hypodermic needle - unless you use the proper shock re-gassing setup, which will be attached to a nitrogen bottle anyhow.

Freeing the adjuster in a turd of a job. I've had some success with over-gassing the shock and then pumping the shock up and down (with the spring removed and adjuster set to full soft).  This only works if the shock still holds pressure, obviously.
Also had some success with very gently tapping the tip of the needle with a punch that fits neatly into the hole in the end of the shaft - the punch has a counter sunk face (quite like a nail punch, now that I think about it). This will burr/bend the very tip of the needle but usually doesn't bend it.

Can't recall what they look like from the other end, but I suspect that it would be the better option.

[oldyzman]

Thanks nathan, i will have a closer look
Brett

[motomaniac]

I heard that he works teams dont use a water trap - it helps keep the shock cool! LOL

[oldyzman]

thanks moto, i will give it a squirt for you
Brett