I've posted this question on a couple of old bike forums as I need to figure out real soon whether I'm going to keep the shock in question. I bought a new shock for my 1981 YZ250 from one of the larger suspension companies that deals with vintage/post vintage bikes. I had an issue with the way the shock fit on the bike and was talking with an engineer at the company about it. Turns out I do need to send the shock back to fix the issue I originally called them about. During that conversation he asked me to check out the rebound dampening and sag before returning it and said it should rebound fairly quickly due the the 81 YZ250 having a falling rate suspension. I checked the sag and rebound dampening after I got off the phone and I could only get about 3 inches of sag when setting on the bike so the spring that came on it is too stiff. The rebound dampening is also wrong because at it's lightest setting it returns very slowly and on it's stiffest rebound setting you might as well get a calendar out to time it. At this point I'm having second thoughts on whether this company knows how to set up a shock for this bike since nothing seems right. In addition to being told the bike had a falling rate suspension, the engineer also said my bike was fairly rare because he knows of only about 5 or 6 shocks they've ever made for an 81 yz250. That seemed very odd to me as I thought it was one of the more popular PV bikes around. After all that....my question IS, does anyone know if the 81 YZ250 rear suspension is a rising rate or falling rate (gets softer as it gets further into the travel). Since I'm not real happy with the way the shock came set up, it would pretty much put me over the edge if it's not actually a falling rate suspension as the engineer indicated.