The slipper clutch is the plate and pads behind the spur gear. There should be three little pads that look like little brake pads. If they are all there, your next item to look at is how tight or loose it is. A properly set slipper should be as follows. Stick an allen wrench in the hole of the shaft that comes through the front of the tranny, with it held secure, try to move the spur gear with your thumb, you should be able to just barely move with some pressure. If it spins easy it's obviously too loose, which sounds like your problem. Could be too that the locknut isn't holding, get a 5mm locknut or you can use loctite if need be til you can get a new one. Also make sure you use the two little concave washers when you put it back together should you take it apart.
