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SiL sliding dog

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

SiL sliding dog

Postby SteveMason » Sun Jun 28, 2020 3:16 pm

Has anyone had trouble selecting gears after fitting a new SiL sliding dog? I did a rebuild on a GP engine and replaced the original part. It’s now very very stiff to select most gears and finding neutral is also a pain. It also makes a sound from the gearbox like a someone shaking a bag of gears when you sit in gear with the clutch in. I’ve never had any problems with gearboxes before. Anyone had this issue?
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Re: SiL sliding dog

Postby Toddy » Sun Jun 28, 2020 3:32 pm

I’ve used original SIL sliding dogs and apart from a little de burring of rough edges never had an issue
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Re: SiL sliding dog

Postby SteveMason » Sun Jun 28, 2020 3:35 pm

Ok, thanks. Can you think of anything else that might cause issues selecting gear? And cause this strange gear rattling noise?
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Re: SiL sliding dog

Postby Toddy » Sun Jun 28, 2020 3:43 pm

SteveMason wrote:Ok, thanks. Can you think of anything else that might cause issues selecting gear? And cause this strange gear rattling noise?


Did you fit an updated selector spring they can make it stiff also did you re shim the gearbox ?
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Re: SiL sliding dog

Postby missing lynx » Sun Jun 28, 2020 6:21 pm

The rattle could be unrelated like a slack chain. Did you check the movement of the sliding dog when you put it on the lay shaft?
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Re: SiL sliding dog

Postby SteveMason » Sun Jun 28, 2020 7:59 pm

Used the old spring and re-shimmed yes.
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Re: SiL sliding dog

Postby SteveMason » Sun Jun 28, 2020 8:02 pm

missing lynx wrote:The rattle could be unrelated like a slack chain. Did you check the movement of the sliding dog when you put it on the lay shaft?


I can’t actually remember if I checked the movement, possibly not. Was rebuilt with new chain guide so I doubt it’s that. Probably best to just strip and check I guess
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Re: SiL sliding dog

Postby Storkfoot » Sun Jun 28, 2020 10:36 pm

The last SIL one I tried to use about 2 or 3 years ago was very badly machined. It was almost impossible to change gear. I replaced it with an Italian one and all was good thereafter.
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Re: SiL sliding dog

Postby SteveMason » Mon Jun 29, 2020 1:09 pm

Really? Sounds like same issue. Ok , thanks
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Re: SiL sliding dog

Postby Warkton Tornado No.1 » Mon Jun 29, 2020 6:40 pm

Personally, I've not found any re-made cursors to be as good as OEM Innocenti or Eibar.

Even the expensive European ones are not made to the OEM standards. They are either manufactured from the wrong material, mis-machined, mis-hardened or a combination of any.

As a consequence, I have literally dozens of cursors & the best solution that I know of is to set up a homemade jig & grind the driving faces of the dogs back to square using old genuine OEM types.

As a 'Club' I would think the issue of poor replacement cursors affects many of us, but if there is a solution, such as commissioning the re-manufacture of cursors, or refacing the working dog faces via metal spraying/grinding back, is it something that should be put into action, sooner rather than later?
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Re: SiL sliding dog

Postby Ken Tucky » Wed Jul 01, 2020 12:50 pm

Interesting thread......................
WT is right, the vagaries in sliding dog selector/cursors means that 'mystery gearbox selection issues' can become a nightmare.
I too, have many 'worn selectors'.
At one time I think that the Taff's, RIP Ian and Terry, had something set up for welding up and refacing the drive dogs, this was many moons ago btw.
As a sprinter, we are looking for perfect gear selection.....................lol..............
So I need undamaged drive dogs on the loose gears..............and it is possible to find reasonable gears still........so far, so good.............
However sliding dogs ..................
Because I have shagged so many selectors (this is not something you would want to be doing on a roadbike all the time btw)..............I take the WT regrind method.
I could not afford to keep putting 'Italian Selectors' in, and found to my pleasure that the SIL ones to be not too bad............
Just to put a scale on this, I put a new or reground selector in for almost every sprint meeting, if we get a load of runs + a knockout, it knocks eight bells of sh*t out of them and the dogs turn to 'globes', with consequent 'gear jumping'.
Of course there is also the damage to clutch drive ears, which also have to be deburred regularly, i.e. the clutch friction material is not worn out, just massive burring, but I've gone off topic now.

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Re: SiL sliding dog

Postby Warkton Tornado No.1 » Wed Jul 01, 2020 2:26 pm

I too can recall that the Frankland Brothers offered a service for re-surfacing cursors.

How they went about doing so, I am unsure, but I am reasonably familiar with metal spraying such as molybdenum, although it's an age since I had any done.

To my mind, there must be some of us think that the recent developments in Lambretta tuning somewhat baffling.

After all, those of us that struggle to find 'standard' components to operate just four gears effectively, must surely be being a bit 'picky' as you never get to hear about any downsides with selection using the current choice of five speed 'boxes..... :?:

Does that mean the manufacture of the five speed cursors is all 'sweetness & light' or are very, very few riding full bore changes with these set ups?

To my mind, the principle of alternative gear manufacturing methods has allowed for five gears strong & wide enough to occupy the space of four could now be best applied to..........(wait for it).........just four gears made using the same principle with correspondingly wider cursor dogs........ ;)

As for clutches, a good solution is to do what the sellers of uprated clutches do. Adapt a motorcycle clutch to fit. I managed to do so & it was excellent.
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