Rebuildable shock ?

[The Prophet of Doom]

What is it that makes a shock rebuildable or not?
Everyone says the xz550 shocks are not rebuildable, but I was rummaging through my parts bins, one had a welded end (near where the label is), and two have what look like screw on ends - like this one on ebay.
http://www.ebay.com/itm/Yamaha-XZ550-XZ-550-Vision-1248-Rear-Suspension-Spring-/360410388104?pt=Motorcycles_Parts_Accessories&hash=item53ea221688&vxp=mtr#ht_500wt_890
Is this a rebuildable shock?

[Rikugun]

That's a good question. If it comes apart I suppose the next hurdle is parts availability. This place sells parts for Ohlins, KYB, and Showa (valving shims, seals, bumbers, etc) as well as offering rebuilding services.
http://www.moto-pro.com/default.asp 

Here's another http://racetech.com/ProductSearch/2/Yamaha/XZ550R/1982-83 Note that under "rear shock products" it specifies the stock shock is non rebuildable. If you had time and felt compelled to ask why, they have a tech line  951-279-6655 x109  Maybe they're only familiar with the welded ones??
Race Tech
1501 Pomona Road
Corona, CA 92880

[Lucky]

I have thought that it might be possable to drill one end of the shock for a small (compression?) fitting & either air charge it or oil/air charge it.  I have no experience with doing anything like this to a shock other than having installed air shocks on my '78 Z28. (i miss that car! lol)

[Rick G]

In the 60's a fellow named Mike Patrick had the number one plate , in AMA district 31 in Socal. He rode a Triumph desert sled. Later he rode a Norton scrambler. One of the problems he had was the regular shock failure (loss of oil) He drilled a small hole and refilled them . 50% were reusable . Just be carefull most shocks now contain nitrogen under pressure.