It appears that you have already tried to move the seat forward or backward by the travel adjust lever. Have you checked to see if the lever is bent? If you are able to tilt the seat forward, check to see if the tracks that the seat travels on are rusty, bent, cracked, or broken. Another thing that you can do, is look at the lower back of the seat and check out the suspension adjust handle. It may be causing some problem also. You stated that the seat's position has not been changed for a long time. If everything appears to be normal, spray some lubricant on the areas and give it time to soak in. It may take some time for the affected parts to move or slide. Sincerely hope that this helps somewhat. Best of Luck.
