Wilsons Sandbox

Well, for the first time I got to ride with some other multi surface riders. We had a great time and a all them were or had been competitive enduro riders. So I learned alot and feel a little more confident off road, but not where I would like to be. Thanks to everyone who shared their advise on the IMS Lever, I had to just bend it out with some vice grips. My next newbie question though, the KLR kicks me in the ass when I go over small drops and jumps. Especially going downhill. One of the Guys I rode with yesterday says I need to adjust the sag. How do I adjust that setting and how do I measure sag on the KLR? Thanks, learning all the time, Mick