You guys are my go-to for this kind of stuff even though I'm mostly a street rider. Spring is right for me, just needs a rebuild and...? https://www.ebay.com/itm/HONDA-CBR1...803540?hash=item3d55d194d4:g:eusAAOSwmuVaWLmW
"The lower bump stopper is missing" There's only two ways that could happen. Either the shock is so old and that rubber just rotted and disintegrated away or someone disassembled the shock and put it back together with that piece missing.
Factor in the refresh cost from a reputable shop with any used shock purchase. If it's still a good deal, and the spring rate is right, go for it. I've had plenty of guys send me shocks that they bought used that ended up within $50 of a new shock by the time they were done with a service and a spring rate swap and whatever "conversion" they wanted.
Not sure, haven't gone far enough to look for someone to rebuild it. I do believe they are still in production though, unlike what the ad says. Seller says they have no info on the bike it came off of, and these bikes often see 100K easily.
