I just reassemble the cable with the twistgrip set in high gear. I simply adjust it up so that the slack has gone out of the small chain, but that it hasn't gone tight when I fiddle with it. Then with the bike upside down on a picnic table in the yard, I work the pedals and gear change. You can tell by the feel whether you have low, mid and high gear. It is usually bang on, and then I do a road test.
I know you are supposed to be able to see an indicator rod through the end of the nut, but on my Merc you can't - at least I'm damned if I can. Maybe I should wear my reading glasses.
As a rule of thumb, if you can't get low gear, the cable is too lose, and if you can't get high gear the cable is too tight.
Last edited by EvilV; 05-07-07 at 08:00 AM.