Simply put, most chain guides don't fit, especially on the 03 model. The swingarm generally hits the guide, or it's a spacing issue. Reason why many of us run homemade guides on them (or heavily modified guides). The MR.Dirt guide is really the only guide that fits without issues. Some run new guides on the earlier versions of the mag's (the ones with the smaller headset stack height are the earlier ones (not the lawwill's, but the earlier single pivots [that came just after the lawwill, but before the 8in stack 100mm BB width ones [[the 2003]]])

Also another thing about his guide is it gets the chain riding higher up, which means that it's not dragging on the swingarm when running a small cog in back. This also allows you to run a smaller chainring up front to keep more in tune with modern times. I myself run a 42t chainring up front, a custom mrp, and profile DJ arms sitting on a custom length profile spindle. I couldn't run my FSA arms due to the fact of me having to basically grind the small ring mounts off if I did. NTM the weight savings wasn't worth the cons of the ordeal.

O and pepper, thanks a bunch for posting this comrade! Your awsome!!!

 fair enough! with the crank arms, i've had to grind off the granny ring mounts on my cranks so i could run a chain guide, pretty irritating, but oh well!

 thanks