Gearbox shimming

[dickie]

Next wee hurdle.

I've used original layshaft and endplate but a new hub bearing. Original shim is 2.0mm. Layshaft is pulled hard into bearing.

When I torque down the endplate the layshaft locks up.

I know I can get 1.6, 1.7 and 1.8mm shims from mb but is there anything else I should look at before I spend another £15 plus postage?

[Wack]

Fit the layshaft without the gears and try. The bearing could be slightly taller trapping the layshaft shim and needle bearing in the bush.

[drivera]

Just had a similar experience although it was building up an engine from bits , turned out the bearing race which is a push fit in the gearbox endplate needed tapping home a tad , did that and the layshaft and gears spun freely

[dickie]

Thanks gents, that was a good help, but I still don't quite know the solution.

Layshaft and endplate fitted only I can spin the Layshaft freely.

Layshaft and shim without the needle bearing, I can just about turn the Layshaft.

It's a new shim and is the correct size at 0.9mm but unfortunately I don't have the original one to measure. The Layshaft is DEFINITELY pulled fully home.

The way I see it is that I could thin the shim on an oilstone, try a new hub bearing or leave the shim out completely.

Opinions please.

[JETEX]

Not sure I'd leave the shim out. Measure the clearance without the shim, and obviously your shim. You can rub the shim down on an oilstone, or take it to an engine re conditioners. The one I used to work at had a magnetic base on their head skimming machine which was great for grinding down things like shims. We used it a lot to grind down overhead cam tappet shims.

[Scooterlam]

Purist and engineers might like to look away,
Like many others I had this issue,
with time running out and a Euro beckoning I spaced the end plate with washers and shimmed up.
Did the euro no issues and rebuilt on return. on rebuilding I removed the washers and it shimmed fine.
making me think that something wasn't fully home, although I would swear the bearing was fully home.
I'm not suggesting for a second that you do the same, but I would remove the bearing and take some accurate measurements of the bearing and the seat refit and accurately determine the bearing is fully home.

[Scooterlam]

No, like OP there was nothing to suggest the bearing wasn't fully home and square.
It's a very late Indian case so it seems anything is possible hence my recent purchase.
It's done another 2 Euros since.

[bluebob]

did you sort it it?put a new bearing in mine,same thing,locked up.got a 1.4 shim.sorted.

[dickie]

did you sort it it?put a new bearing in mine,same thing,locked up.got a 1.4 shim.sorted.

Almost sorted. I removed and refitted the layshaft and I can now spin the gearbox freely as long as I don't fit the big shim (mine is 2.0mm). I couldn't see anything stopping it from pulling fully home, but I guess there must have been something as it's OK now.

I'm struggling to measure the gap as it is, but as I type I've decided to try some 2.0mm solder which I use for squish measurement. I'll put a piece either side to stop it rocking to one side and giving a false measurement.

Where did you get a 1.4mm shim? 1.6mm from mb is the smallest I can find.

[dscscotty]

Cylcones 5 speed come with shims down to 0.8 so Rimini Lambretta may have some, or I can send you some?

[dickie]

Cylcones 5 speed come with shims down to 0.8 so Rimini Lambretta may have some, or I can send you some?

Cheers scotty, appreciate the offer. I've measured just under 1.8 using solder as plastigauge so I'll get 1.6 and 1.7 from mb. I've also found that Mike phoenix does them down to 1.2mm.

I'm not 100% confident in my method but I'll soon see.

Thanks again for the offer.

[Warkton Tornado No.1]

You may be aware of this trick, but to speed up the process of ‘shimming’ you can leave the cluster out until final assembly.

Just fitting the endplate on & off with different shims is a pain, but, if the cluster is left out for the process it becomes far less tedious…

I hope this "inane wittering" is of some help to somebody

[dickie]

In case it's some use to someone this is how I measured my shim gap.

First technique I tried was no good as the solder just got jammed between the layshaft race and the layshaft itself.


So I did this. Held it in place with a blob of grease.


As my gap was just under 1.8 and my solder is 2.0mm the crushed part is only just visible. This technique has the limitation of needing the solder to be just a little thicker than the gap, but it's still useful at times.