Gearbox layshaft height challenge

[Topgearskin]

A little knowledge is a dangerous thing.

Having swapped everything from a knackered Indian casing into a good Italian LI casing, I've now discovered a gearbox issue.
When shimming up I've had to use a 2.6mm shim. And although I'm a little over on the gap, the gearbox won't turn once the endplate is torqued up.
Reading the bible ( stickys book) I've discovered that the gears should sit above the layshaft... and typica
Lay with this build, mine don't.
I've been trying to use some LI150 gears. Even when I've bit the bullet and tried the old Indian gp150 oddball gears that came with the bike, the story remains the same.
So now what? Buy a new gearbox? (And miss the chance to use a desirable LI 150 box - or does anyone know which layshaft will remove this problem?
This bike has been a delight, I have to say. I'm running (eventually) a Gori 200, 18x46, 22 scootopia carb and AF clubman,

[Knowledge]

Have you tried a different layshaft? You seem to have tried variations on everything else.

[Topgearskin]

Not as yet. I Was hoping that there was a magic secret, like "the layshaft made by ..... are designed to get over this issue" or "use a bigger shim" or something.

[rossclark]

A bigger shim won't help. A different layshaft might. It is possible either the shaft or the gears could be worn causing it to sit lower.

I've heard it said that you can apparently put a shim under the stack to raise them a bit.

[Wack]

The LI box is always on the limit for some reason so to get around it if different layshafts don't help is to machine the area down where the shim fits on the layshaft to end up 0.1 mm lower than the gears.

[Strummer10]

We had the same problem on my mates series 4 and whoever shimmed it before hadn't checked it out properly so it ended up with the layshaft biting into the shim and carving out a round slot. Surprisingly it ran for 12 years with this issue.

We played around with different gearboxes onto the layshaft but with no success and had to change it for another 2nd hand layshaft. I suspect it would be a quicker and maybe just as economical fix to buy a new layshaft.

[Topgearskin]

Thanks everybody. It's certainly been a journey, this one.

[Delboyli150]

Sorry in case you already have done.....but you have put the rear hub on and tighten up...

[corrado]

Had you used the Li150 gearbox previously or was it new to you? Some "new" Indian Li 150 boxes on the market that suffer with this problem.

[Topgearskin]

The gearbox and layshaft were in another casing built buy a mate of mine from Manchester. I had ran the casing and gearbox with a mugello a few years back and it was golden. The Indian casing had a GP150 box in and the layshaft wasn't great either....

[Adam_Winstone]

Regardless of the shimming, this isn't just a case of the very common issue of endplate locking Christmas tree until the clutch centre nut is done up to pull the Xmas tree fully home into the endplate bearing is it? It is very normal (more often than not) for the gearbox to lock up when the endplate is fitted. Then fit the clutch centre and nut so that it pulls the Xmas tree home and the gearbox becomes free, then remove clutch nut and centre and tighten the 6 endplate nuts again.

Whilst the shimming issue is annoying, I imagine that there are many motors out there running perfectly reliably with the same issue.

Good luck.

Adam

[gaz_powell]

TGS did you get this sorted ???

[Topgearskin]

I think so
I replaced the gearbox with a new SIL GP200. There is now about 1mm gap. This appears to be fine.