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Gearbox / layshaft shimming issue.

Technical help for Series one, two and three Lambrettas. Models include the Li, Li Special, TV, SX, GP, Serveta and API/SIL models

Gearbox / layshaft shimming issue.

Postby corrado » Mon Nov 19, 2018 10:52 pm

I've got a close ratio gearbox that when assembled correctly on a layshaft sits below the top of the layshaft. Hence I'm unable to shim it. I've got a selection of layshafts, Casa, FA Italia, MB, Sil, all with the same issue (a pacemaker gearbox works fine with all of them though). I've also got a couple of unknown branded layshafts that line up ok with the c/r gearbox but I'm a bit reluctant to use them in a tuned engine. Looking in Stickey's 3rd edition he mentions grinding down part of the layshaft close to where the oil seal goes. Page 81. I can't get my head around how this might help, as even if it allows the layshaft to be pulled through the bearing further it'll just take the gears with it I presume? It would seem more logical to turn down the top of the layshaft slight so that the gears sit higher but that would be too easy so I'm not seeing the obvious error of going that route. Anybody have any constructive comments to add?
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Re: Gearbox / layshaft shimming issue.

Postby ULC Soulagent » Mon Nov 19, 2018 11:05 pm

have you tried flipping the loose gears the other way round maybe
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Re: Gearbox / layshaft shimming issue.

Postby ULC Soulagent » Tue Nov 20, 2018 6:07 am

The grinding of the layshaft on page 81 refers too the middle pic and not the bottom pic with the o-ring seal.
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Re: Gearbox / layshaft shimming issue.

Postby HxPaul » Tue Nov 20, 2018 11:41 am

corrado wrote:It would seem more logical to turn down the top of the layshaft slightly so that the gears sit higher


+1
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Re: Gearbox / layshaft shimming issue.

Postby corrado » Tue Nov 20, 2018 2:20 pm

ULC Soulagent wrote:The grinding of the layshaft on page 81 refers too the middle pic and not the bottom pic with the o-ring seal.


Doh, it makes sense now, I only saw one pen. :oops:
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Re: Gearbox / layshaft shimming issue.

Postby ULC Soulagent » Tue Nov 20, 2018 10:09 pm

Hope u get it sorted ;)
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Re: Gearbox / layshaft shimming issue.

Postby dscscotty » Tue Nov 20, 2018 10:17 pm

what make/manufacturer of the gearbox?
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Re: Gearbox / layshaft shimming issue.

Postby corrado » Wed Nov 21, 2018 2:16 am

dscscotty wrote:what make/manufacturer of the gearbox?


It came via Italy but presumed Indian. SX200 1st, 2nd, 3rd with Li 150 4th. Same ratios as one made by DRT but no markings on it.
1/49 - 2/40 - 3/37 - 4/34 + 12-14-17-20
I was planning on trying it in place of my Li150.
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Re: Gearbox / layshaft shimming issue.

Postby hullygully » Wed Nov 21, 2018 3:24 pm

think Broady & Cyclone do a shim that goes inbetween the loose gears & rear hub brg :shock:
soz it goes between the layshaft & brg derrrrrrrrrrrrr :roll:
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Re: Gearbox / layshaft shimming issue.

Postby gp200ts1 » Thu Nov 22, 2018 8:13 pm

A shim between the layshaft and bearing won’t help as it will not change the layshaft to gears clearance. You would need a shim that sits under the gears between them and the shaft.
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Re: Gearbox / layshaft shimming issue.

Postby gaz_powell » Thu Nov 22, 2018 10:10 pm

AF do a shim for under the loose gears and the bearing
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