Does anyone know what oil weight / grade should go in the rear shock of a Mk2? I am doing the rebuild myself because I am a tight yorkshireman, and it seemed like fun.
So far it seems really very straightforward.

How much do you weigh?

[b]scrubs :[/b]
> How much do you weigh?

About 2st more than I should.
13st.

[b]andypugh :[/b]
> Does anyone know what oil weight / grade should go in the rear shock of a Mk2?
> I am doing the rebuild myself because I am a tight yorkshireman, and it seemed
> like fun.
> So far it seems really very straightforward.

Didn't know we could re-build them ourselves How do we do that then Cheapest quote i got for a re-build was £100

me neither come on andy spill the beans
cheapest quote iv had was £80 from k-tech

[b]mickstoy :[/b]
> me neither come on andy spill the beans
> cheapest quote iv had was £80 from k-tech

Think it's time to get your head mechanic out with his disc cutter and welder Mick

i was thinkin that mate itl give him something to do i dont think he's got enough projects on the go at the moment

[b]andypugh :[/b]
> [b]scrubs :[/b]
>> How much do you weigh?
>
> About 2st more than I should.
> 13st.


I would go for a 3.5 weight.

I think the standard is 2.5 but some people complain about that being too
soft.

If you're going to get a new spring - based on your weight - go for a 5.4kg
or nearest suitable match.

I'm sure when I had my shock done (K&S racing) as well as filling it with oil, they also had to presurise it with gas (nitrogen?) I am not sure how they put the gas in but I doubt it would be a DIY job?

quoth Gwyn

> Didn't know we could re-build them ourselves How do we do that
> then

Well, let me finish the job to see how it goes first, but so far...

1) Release any pressure remaining in the reservoir (it's a Schrader valve)
2) Unbolt the banjo holding the reservoir on. Pour out all the congrungulate formerly known as oil.
3) Unscrew the preload collars right off the end. The spring then comes off with no need for compressors or special tools.
4) Remove the cap from the seal end of the shock. It has two holes. I made a nice pin spanner to unscrew it, then found it is just a push-fit. So just put a 3mm pin in each hole then strike the pins with drift to evenly push the cap off.
5) This reveals the seal head assembly. Push this into the shock body to reveal the retaining clip. I did this by cutting a bit of plastic pipe, slitting it down the length, slipping it over the piston-rod under theend cap, and tapping the piston-rod into the shock body with a soft mallet. But mainly because I had a bit of plastic pipe next to the vice and it was the first thing I saw. Remove the clip.
6) Pull the whole lot out. The O-Ring tends to hang up in the circlip groove, so you need to pull quite hard.
7) Unscrew the piston nut from the piston rod. I believe they are staked when new, but mine had been rebuilt once already and it just unscrewed. If it has been staked you will need to grind off the staking.
8) lift off the piston components, thread a cable tie through the middle to keep orientation and order.
9) ...

And that is as far as I have got so far. I anticipate a bit of a faff getting it totally full of oil, but i have a few ideas and will see what works.
It needs pressurising with nitrogen to what sounds like a scary pressure, but it is no more than my bicycle tyres are pumped up to. And I work with fuel systems running at 20,000 psi so may be a bit blasee.
As it happens, I don't have any nitrogen (well, I have a garage-full, but contaminated with oxygen, argon, CO2 and spiders webs). I do, however, have pure argon for my TIG welder. I intend using that. I will probably use the £5 12V compressor/tyre inflator with its inlet plumbed directly to the output of the welding regulator.

As for a remark elsewhere about it not being a DIY job, anything can be a DIY job if you want to badly enough. You should see the pannier mounts on my R1 using brackets I 3D-printed using a 3D-printer I made out of an old flat bed plotter and a bit of home-brewed software. But then I have always seen "No User Servicable Part Inside" as a challenge.

So far the shock rebuild is looking simpler than some fork rebuilds I have done. Fewer "Gotchas" than the FJ1100 forks, for example.

I have also dismantled a shock in the same way as explained above but mine being a Mk1 does not have a Schrader valve so I have no way of getting gas back in to it!
I would be interested in knowing how they charge a shock without using a Schrader valve?

Well, the shock is back together, I will test ride it tomorrow.
Cost was £24 for the seal head and £7 for the oil.
The seal head assembly on the Mk2 is the same as the CR250 from 1989.
Part number 29-661.A from
http://www.oro2u.com/acatalog/250cc_HON ... _KITS.html

I used a 2:1 mix of 2.5 wt and 5 wt suspension fluid. Time will tell if that was right.

1) Release any pressure remaining in the reservoir (it's a Schrader valve)
2) Unbolt the banjo holding the reservoir on. Pour out all the congrungulate formerly known as oil.
3) Unscrew the preload collars right off the end. The spring then comes off with no need for compressors or special tools.
4) Remove the cap from the seal end of the shock. It has two holes. I made a nice pin spanner to unscrew it, then found it is just a push-fit. So just put a 3mm pin in each hole then strike the pins with drift to evenly push the cap off.
5) This reveals the seal head assembly. Push this into the shock body to reveal the retaining clip. I did this by cutting a bit of plastic pipe, slitting it down the length, slipping it over the piston-rod under theend cap, and tapping the piston-rod into the shock body with a soft mallet. But mainly because I had a bit of plastic pipe next to the vice and it was the first thing I saw. Remove the clip.
6) Pull the whole lot out. The O-Ring tends to hang up in the circlip groove, so you need to pull quite hard.
7) Unscrew the piston nut from the piston rod. I believe they are staked when new, but mine had been rebuilt once already and it just unscrewed. If it has been staked you will need to grind off the staking.
8) lift off the piston components, thread a cable tie through the middle to keep orientation and order. Make a note of which is nut side and which rod-side. (the thicker washer was rod-side on mine)
9) Remove the seal head from the piston rod.
10) Clean everything. I used white spirit. I use a lot of that cleaning bikes, it shifts chain lube brilliantly.
11) Re-fit the spring seat and bump-stop. Thread the end cap onto the rod.
12) Fit the new seal head and the piston stack. Re-fit the nut using Loctite. I did mine to 24lbs ft, but that was just the number I got from the web for a KLR650. Bear in mind that if that nut comes off, bad things happen.
13) Temporarily re-fit the reservoir. (or a blanking plug)
14) With the shock body held in a vice, pour a bit of suspension oil into the body. Push the piston in and through this oil.
15) After oiling it's O-ring, push the seal head home. At this point the bit of plastic pipe mentioned above really came into its own, as it let me press quite hard. Placed between the end-cap and the seal head it lets you push the seal home using the end-clevis.
16) When the O-Ring of the seal head hits the edge of the shock body you will get a hydraulic lock. To release this, remove the compression adjuster from the reservoir. A washing up bowl under the vice is a good idea around now to catch the oil and to save the living room carpet. It is probably still quite a tight fit, so I wrapped a ratchet-strap round the shock and pulled it into place that way.
17) Push the seal head a little way past the circlip groove then fit the circlip. Pull the rod up to seat the seal head against the circlip,
18) Now with the shock in the as-installed poition in the vice remove the reservoir banjo. Fully compress the shock and pour oil into the banjo hole until it is full. Now work the shock up and down a few times to purge any air from the system.
19) Fully extend the shock and top-up the oil level in the body through the banjo hole.
20) Put the spring and the preload collars onto the shock, but don't screw them onto the thread. Make sure that you get the collars the right way round, they both have a right way and a wrong way. You willl curse if you get the shock all bled-up and ready to go then find that the top collar is the wrong way round. I did.
21) Attach the reservoir.
22) This is a tedious bit. You need to add oil into the compression adjusting cavity, work the shock up and down, add some more, etc, until you feel you have fully "burped" the system. Getting air out of the lower reservoir (gas bladder) chamber is important, and a bit of a faff. You might want to hold your thumb (if fat enough) over the compression adjuster opening and work the shock up and down with the reservoir in a number of orientations.
23) Next stage is to empty the bladder of air. Extend the shock while keeping the compression adjuster cavity full. * Fit the adjuster, letting it sink into place under it's own weight so that you don't push air into it. screw it in tightly enough to make a seal. Compress the shock, then push the vlave core in. There will be a little hiss. Remove the adjuster, extend the shock while topping up, repeat from * until you get bored. Finsh with the compression adjuster screwed in.
24) Now for the final bleed. Push the schrader valve core in, then loosen the compression adjuster unit until oil oozes out. The bladder will expand to its natural volume and should push out the last bit of air trapped in the compression adjuster.
25) Fill the reservoir to the correct pressure with dry nitrogen. I didn't have any, so I connected the outlet of my TIG welder regulator to the input of one of those £5 300psi tyre inflators, and pumped up to 120psi with pure argon instead. It worked like a charm.

There you have it. It's a long list of steps, but that is partly verbosity on my part. I do not claim to be any sort of expert, this is the first time I have ever even thought of rebuilding a rear shock. My procedure was a modification of advice for other types of shocks from
http://calgarydualsport.tripod.com/klr6 ... edure.html
and
http://www.mx-tech.com/downloads/Showa_shock.pdf

Have fun.

Andy Pugh

Nice one Andy 8) I think that is going to be really usefull in the near future. Thanks mate

F**k, im impressed , Looks like I have another winter job. I did my forks earlier this year, I might as well do the rear. ( Can't wait for the cursing and swearing)

Good Work!

He who dares Rodney......