Scooterotica

what would cause the big shim under the end plate which is ontop of the loose gears to ware a grove in one side but yet not on the other

Possibly not shimed correctly in the first place?if the needle bearing in the end plate is worn/broken that will let layshaft move about. An adult will be along soon hope this is of some help.

As Craig H said,incorrectly shimed gearbox mate and the reason it only wears on the one side is because the gearbox shim is tight against the loose first gear and so moves round with it,but the other side is tight against the outer face of the layshaft end plate bush and thus wears a groove as the gearbox end plate dont move,there is a correct gap required,i belive it to be 0.07mm to 0.30mm of the top of my head,if its not set up correctly it will expand with heat and with no gap to expand its jams and a groove is cut.Stickys book is the way forward for gearbox shimming etc.Hope this Helps mate.

Refereance my last post,ive just read it and it should read.Its the machined part of the endplate in which the layshaft end plate bearing bush sits that causes the groove and not the bush its self

thanks to all for the reply`s, i know should have checked the book,what a plonker