Sachs rear shock service?

[Jbeta300]

Have a rear shock off a 300 that I was thinking about servicing? Bike has 120 hours, should I change the oil or leave it? Other than nitrogen, can I do with basic tools?

[Timber]

Service it. Sachs shock is pretty strait forward.

[twowheels]

Have a rear shock off a 300 that I was thinking about servicing? Bike has 120 hours, should I change the oil or leave it? Other than nitrogen, can I do with basic tools?

Service it ... about 60 hours ago

[Arctra]

Here's my notes which might help you - I have copied them from various places so can't take credit really. The 2010 Husqvarna TE450 workshop manual actually has a very very good section on servicing the Sachs shock if you feel like googling it (Section J of the manual is what you're after).

You'll need:
- a vice with aluminium (or "aluminum" for you Yanks out there) jaws to make sure you don't damage the shock.
- a decent circlip pick is needed to remove the circlips. The manual says you can use 2 screw drivers, which is correct, but a pick makes it heaps easier. Rather than trying to pull the clip up at first, push it down near the gap in the clip. Once half of it is out of the groove it's much easier to then pull the other half up and then the whole clip out.
- a Gasket Scraper or slightly blunted wood chisel makes getting the shock absorber cover off easier.

Be careful when pulling the piston and forkrod unit out as it pops out once the O-ring gets past the circlip groove. It's quite easy to hit yourself in the face if you aren't careful. On one video I thought it was quite a good idea the guy had, he actually secured the top of the shock in the vice jaws with the shock hanging to the ground with an oil pan under it. He then put a bar through the bottom shock holed and knocked it with a rubber mallet to get the piston out.

I wasn't going to bother disassembling the piston unit, but I'm glad I did. There is quite a bit of dirty oil trapped between the shims that needs to be cleaned out with a degreaser first, then some brake cleaner followed by a blast of pressure air to remove any residue. You can either put a screwdriver or a loop of wire on the end of the rod and pull the whole shim stack and piston assembly onto it to keep everything in order while you clean it. When cleaning make sure you get in between each shim. Put the nut back on torque it to 25Nm and Green Loctite.

Before reassembling everything I made sure I cleaned both inside and outside with degreaser, then brake cleaner followed by a blast of air.

The manual says to top up the shock absorber body with fresh oil first, but my tuner recommended filling the reservoir first. Fill it up to the brim (no need to measure a set amount) then put the diaphragm making sure you don't trap any air - which you shouldn't if you fill the reservoir to the brim. Put some grease on the O-ring on the diaphragm to make it slide in easier and squeeze some air out of the diaphragm so it is not collapsed, but not totally squashed either. This will allow a little extra oil in the reservoir and mean you won't need too much air/nitrogen in it. Push the diaphragm down until oil appears in the shock body. This way you can be pretty sure you've forced all the air from the compression adjustment parts.

Once you've done that, put the reservoir plug back in and make sure you put the circlip back in place otherwise it'll pop off when you push the piston in.

Top up the shock body up with oil then push the piston assembly in. There will be resistance so you need to keep releasing air pressure from the reservoirs valve.

Push the piston down fairly gently so it is well covered by oil, then move the piston up and down slowly. You should see air bubbles coming up. Once no more bubbled are coming up, pull the piston up to a couple of cm's (just under 1") from the top of the shock body, making sure it is still covered with oil. Tap the top of the shock rod firmly (but not too hard) to cause sufficient shock to force oil past the shims. You should see more air bubbles rise when you do this. Do it several times till no more air bubbles rise. Now you can be pretty sure there's no air left in the system.

Top the oil off to the circlip groove in the shock body and push down on the rod making sufficient pressure is released from the reservoir valve to allow the circlip groove to be seen in the shock body. Now put the shock cover and push it down until you can see the circlip groove - it may require releasing pressure from the reservoir valve to so this. Once you can see the groove, insert the circlip to the cover is secure.

Now using a low pressure pump (like a bicycle pump) put air into the reservoir valve until the shock cover seats itself on the circlip securely. Probably around 40-50psi. Once it is seated properly, release the air from the valve then get it charged with Nitrogen. The manual says 10-12 bar of Nitrogen which is quite a wide range. My tuner charged it to 150psi which is just under 11bar. I actually don't use nitrogen, I just use my high pressure fork pump to pump it to 160psi as a very little bit of pressure is released when I remove the pump from the valve. Chatting with my tuner he reckons it won't make a big difference and there should be no problem using regular air (which is over 70% nitrogen anyway).

You can now push the shock rod down and it should slowly push its way out on its own.

One of the issues I had was that I could not find any "Shock Oil" at my motorcycle shops so I didn't know what to use. My tuner has done some pretty extensive testing on a shock dyno with various oils and has determined the Motorex 5W Fork oil (yes, FORK oil) is stable enough to use and performs well. So that's what I used. The important thing with whatever oil you choose is its viscosity (measured in Centi Strokes - cSt) and not its "weight" rating.

Sounds like it's quite a job but you can knock it over in a hour or so if you have everything prepared. I'm glad I've learned how to do it now and will be servicing the shock every 12 months from now on. Apparently by the end or 12 months the viscosity index improvers in the oil have significantly broken down and so the viscosity when the oil heats up is wrong for your damping circuits.

[twowheels]

You may want to consult the Sachs manual posted on the Betausa.com "Support" page.

[mtnmanseth]

Helpful thread, thanks guys

[Marty Moose]

You may want to consult the Sachs manual posted on the Betausa.com "Support" page.

Yep I would too the std shock doesn't have a bladder as the above thread, there are a couple of important steps not listed.

MM

[icejojo]

Hi,
Could someone describe me the process of refilling oil in sahs shock and how to get rid of air, I have studied service manual but there is written that i should take off the part where is compresion adjuster (it is attached to linkage). I dint want to do this. Is there any other option to refill oil and get rid of air? How much oil should i put in? Thx M

[JoeMaico]

Rather than starting a new thread, I will post my question that deals with replacement parts here. For a 2016 Sachs rear shock, when doing a routine service (replacing the oil and performing a general clean up) - what parts need to be replaced? Reading the manual, they only replaced a Teflon band and an O-ring upon disassembly of the Piston. I assume you should clean out the shim stack as someone suggested, but that does not require dissembling the piston. The Shock has 140 hours on it and has never been serviced. Should I just go ahead and order the gasket Set (#5) and the piston set (#7) before starting? Are there other wear items that should be replaced at 140 hours?

joe

[mike307]

Hey joe , on my 16 250rr i am doing the job at home , every 40-50 hours , thats for me 2 oil changes , and off season a big overhaull , oil ,seals and orings . every time you are servicing it check the body for wear .. my shock body lasted 200 hours ..