I have a 1999 Skidoo 670 MXZ. I got it as a wreck, and have been doing repairs for the last few months. After re-installing the track and rear suspension, I noticed that the travel of the rear swing arm assembly is odd. It moves down about four inches with only moderate pressure, and then seems to stop. After this I can hardly get the suspension to move at all. There is a bolt that stops the motion of the two swing arms at mid travel. I cant figure out if this is to transmit motion or energy to the front arm, or change the dynamics of the rear arm. It looks like it is adjustable to allow more or less travel. Any ideas about its purpose, or adjustment? Any info would help. Thanks!