I've been running the same three Horstman Greased Lightening clutches on various flathead and Animal engines for a total of about 8 years (they run in rotation; it's quicker to change the whole clutch than to change drivers when I go to a different track or change engines); the instructions give you the clearance ranges, so you clean them after every race day and measure them regularly with a feeler gage. When the clearance between the friction plates and the steel plates is excessive you rebuild. Haven't had to toss one yet, though they get rebuilt at least once a season. The measurements will tell you when it's time. All have aftermarket steel baskets, so getting notches from the teeth on the disks hasn't been a problem. I have a spare clutch that has an aluminum basket, but it has the steel clip-in inserts, so it doesn't get notches either. So far it's been a replace what's warn and carry on proposition, so my only problem is that GL parts are getting harder to find, so I may have to go to a newer design. Oh, yeah; in addition to notches in the basket requiring basket replacement, if the steel disks warp, they need replacing, and they need to be de-glazed periodically on fine emory cloth on a surface plate; plate glass works fine (a piece of 3/8" or thicker about 12"x18") if you don't have access to a machine shop type surface plate. I've found that there is a wealth of information that comes in the instruction sheets for kart clutches, so squirrel them away in or with your log book; the instructions will give you the info you need ot know to determine when to rebuild and a lot of other things you need to know. Definitely a case of, "When all else fails, read the directions." If you bought used and have no directions, contact the manufacturer and get them if you don't know someone at the track with a set that they can copy for you.
