I have a 2002 Yamaha XLT800. I fell off it while riding it. When I climbed back on, all it did was make a clunk sound. I put a screw driver across the starter relay contacts and it made the same clunk (knock). I opened up the intake grill on the bottom of the ski to get to the impeller shaft. It will rotate one revolution and stop and back the other way and stop like it is hitting something. If I turn the shaft as far as it can go in the wrong direction and hit the starter, it will spin one revolution till it "hits".