What to do... S4 shock refurbishment

[Mr Earl]

So I bought a used S4 shock (as an upgrade for my M800) on that auction site for pretty cheap.  It arrived Friday, and it has cosmetic but widespread surface corrosion on the main cylinder and on the preload threads.  Maybe more importantly, it is missing the stop bumper pad found at the base of the shock.  Also, the spring has a few nicks and is not glossy anymore.  The shock doesn't leak as far as I can tell.

The seller will refund the purchase price (not shipping, of course) if I return the unit.

I'm thinking of disassembling the shock and powdercoating and/or painting the corroded parts, replacing the spring and the bump pad.

So my questions are:

What's the procedure for disassembling the shock?  I haven't found anything here or on the web.

Can I use this http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=3980spring compressor?

When/if I remove the spring, is a nitrogen refill required?  Who does that?

Are new bump pads available anywhere?

Can I use the spring from my M800 on this shock?  Alternatively, what are some options for replacement springs?

And the most important question:  Is refurbishing this thing worth it, or should I just return it?  Keep in mind that there's no way I can consider a Penske/Ohlins/Other aftermarket shock - marital congeniality is at risk.

Thanks for all opinions.

[caperix]

What kind of shock is it?  Most of the Showa units are rebuildable, while most of the Sachs units are not.  The spring is more than likely not correct for your weight any ways, good sites to check out are racetech & traxxsion dynamics.  No FHE with an S4 shock but I'm sure someone else can let you know more info on it.

[Mr Earl]

What kind of shock is it?  Most of the Showa units are rebuildable, while most of the Sachs units are not.  The spring is more than likely not correct for your weight any ways, good sites to check out are racetech & traxxsion dynamics.  No FHE with an S4 shock but I'm sure someone else can let you know more info on it.

Sorry - it's the Sachs fully adjustable unit.  I'm not concerned with completely rebuilding it, just what's involved with spring removal.  I weigh about 175, and am on track to hit 170.  I think either stock spring (the M800 one or the S4 one) will be fine.  I don't plan to go to the track (maybe on a lark) so a stiff spring is not required.

[Howie]

Before doing anything make sure the chrome on the shaft is not worn or nicked.  If it is, the shock is garbage.  If you plan on powdercoating the shock will need to be rebuilt.  The Sachs shock can be rebuilt, but finding the parts will be difficult if not impossible.  If I remember correctly, you will need to relocate an ignition coil to make room for the reservoir, an easy enough task, but, IMO, one more chore to fit an old corroded shock.  You might want to give Traxxion Dynamics a call.

[Mr Earl]

Thanks, Howie.

The shaft appears to be in perfect condition - nice and shiny, no nicks, corrosion, or roughness.

The coil on the M800 is on the left side under the side cover, so no interference there.  As best as I can tell by holding the shock in position and eyeballing, there will be no interference.

If I can get the spring off, I can get at the main cylinder, resurface it and paint it.

The other big issue is the bumper, not sure how to get a replacement on the shaft.  Does the bottom end of the shock disassemble readily and allow access to the shaft?  Race Tech lists replacement bumpers (the web site says "Call")

Has anybody done this disassembly?  Any schematics out there?  Thanks.

[He Man]

without actually seeing the unit, i cant really say much... but from the 4 shocks i've had on hand, they all are a bit different.

I have the harbor freight tool, but you have to "customize" it to get it to work since its made for car springs, not small motorcycle springs.

[Speeddog]

That shock will bolt on to an M800.

The OEM S4 spring will be *OK*, the OEM M800 spring is a bit lighter AFAIK.
You would be better off with a spring that's proper for your weight.

The lack of a bump stop rubber is an issue.
I don't think you can remove the end without depressurizing the shock first.

I think that Ducvet (http://ducatimonsterforum.org/index.php?topic=18933.0) has done work on those Sachs shocks.