yeah, something's seriously wrong here. Previous owner had no idea about bikes in general he didn't even notice the chain had about 4 inches slack so I doubt I get any info from him.
I checked the upper and lower bolts, and everything looks right. Also I double-checked the collar for preload setting and everything looks correct. I set it to 7, and it sits right there on the highest notch.
Static sag- will have to do some measurements tonight but with bike on side stand, the clear rod coming out of the damper (sorry I don't know the specific term here) is about 1.5 inches long. So the whole thing has 1.5 inches total travel and that is with me off the bike!
I'm kind of puzzled by this but I guess what it boils down to is either a used stock shock off ebay or a proper ohlins/racetech/penske.
Strangely enough the front seems perfectly fine.
A fully assembled factory shock/spring unit at full extension has about 26 mm (1 inch = 25.4 mm) of bare shock shaft exposed to the eye. The shaft mounted snubber at the bottom eye end of the shock adds some more stroke length when it's engaged in a bottom out scenario.
So, your total 4.7 inches of vertical wheel travel comes from the axle being as far as it is from the swing arm pivot point, the bare shock shaft length, and the snubber compression.
If you are getting a "clunk" at full compression, I have to wonder if the snubber is gone or badly rotted to the point of uselessness.
If the snubber is gone, that could be suggestive that someone took the shock off and disassembled it.
IF they did, maybe they forgot the spring centreing washer that rests between the spring end and the preload collar.
In which case the installed spring height will be wrong, with the spring loading up on the preload collar.
AND if a butcher was involved, maybe they attempted or succeeded in removing the reservoir and unwittingly broke into the sealed gas charged hydraulics.
KarlJay just posted shortly ago and suggested removing the shock to allow full and unhindered inspection.
It's an easy job to do, and would permit proper inspection.
Clearly, something is not right.