lambretta gp gearbox

[steve kirk]

i'm currently building a gp200 and am having problems with the gearbox.It's standard 200 and it's jumping out of first gear and there's a false neutral in 3rd.I've replaced the sliding dog the gear selector arm and have put an uprated spring in the layshaft.Before you ask yes the gears are in the correct way round and the gearbox is correctly shimmed.The only thing i have'nt changed is the wishbone and the paws,but even with all these changes it's still no different.I have stripped and rebuilt this gearbox several times now and as you can probably understand it feels like i'm banging my head against a brick wall so would relly appreciate any advice you can give me thanks.

[wack 63]

First of all have you checked the gears are taller than the layshaft as if not the sliding dog will hit the shim and not be able to fully engage,then check the condition of the internal dogs on the gears in question as any roundness or chips won't help. Check the mesh with the cluster and the teeth on the cluster for wear,cracks or chips.Remove the wishbone and lay flat to check both legs are even and the pawl holes are not elongated. Finally check the handlebar gear change can move far enough to select 1st as a trapped clutch cable can stop full movement and that the swivel on the engine is not worn and the cable outers have free play for suspension movements. Can't think of anymore at moment