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G: Gearbox Vincent twin gearbox clearance set up



craig

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VOC Member
What am I missing in instructions to set up an E76 shim onto G3 shaft to get proper clearance or alignment of the gearbox?
I am not finding any reference.

What is the proper sequence for selecting the proper shim or set of shims for E76.??

I am not showing the G2 gearbox cover plate and E91 bearing.

Should I set this up vertically with G3 and G5 shafts installed in G2 plate and shim G6 pinion until it matches G7?
Or is it more complex than that?
Cheers
Craig

GearSetDrawing1TV.jpg
 
Last edited:

chankly bore

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VOC Member
Be aware that G11 double gears (all variants) had their width altered to 2.595" in 1954 as per Workshop Instructions, so don't assume interchangeability.
 

greg brillus

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VOC Member
The clearance is more about the two shafts G3 input and G4 output. This allows oil to get to the bushes within the G4 output shaft. If the clearance is minimal then this will limit oil and the bushes can seize, remembering that the oil level in the gearbox is not up at this level unless you over fill it. You could carry out a partial assembly without the gears except for the G6 gear pressed onto the G3 shaft. The G2 cover complete with bearing, lockring all in place. Then bump the cover home into its recess this with the G3 shaft installed through the bearing, and check for inward/outward movement of the shaft, then screw in a couple of the cover screws to pull the cover fully home and check again. It is possible to have almost nil clearance with no shim installed, this can require a small amount taken off the face of the G4 shaft, but this is usually if the crankcases have had their surfaces skimmed after weld repairs or similar. If the shaft moves more than say 20 thou, then add shims as required, you want at least 10 thou and no less..........There is no set guidelines as each engine /shaft combination is different. Be sure that the G2 cover is pulled up fully home when you check this even if you use more screws to pull the cover home. With the screws removed just give the Right hand end of the G3 shaft a nice tap with a soft face hammer to remove the cover/shaft from the crankcase mouth. It would pay to do one final check of this again with the complete gearset in place just to be sure. Good luck with it all.
 

greg brillus

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VOC Member
Sorry Craig, I forgot to mention that you need to have the output shaft and sprocket, nut etc in place and done up firmly first before you carry this out so the output shaft is fully in place. Not sure if you are using original gears or new ones, but if some or all are new you need to do a dry fit of them on their respective shafts and check for any tight spots/binding..........this is very common and I have found i have had to grind off the tops of the dogs so they will slide into their mating gear without binding. It would be a disaster to fully assemble one and hope it all works straight away. I am currently assembling up a brand new engine of all new parts and the gearbox has several tight spots that would make it near impossible to select gears smoothly. Lots to look at, and never assume all will be well without a trial fit and checks first. Cheers and good luck.............Greg.
 

greg brillus

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VOC Member
If anyone was contemplating fitting a starter kit to a twin, it would be a good idea to trim a small amount off the right hand end of the G4 shaft, say 1 to 1.5 mm at most and no more. This might assist with the installation of the kit for a touch more clearance for the starter pinion where there is very little room for the ratchet to function on some. Each installation is that bit different, and some are very tight in this area ............ Just a tip that might help.
 

john998

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VOC Member
Having had the bushes in G4 collapse I drill 4, 1 mm holes in the tapered end of G4 to ensure oil gets in. In my gearbox G6 had to be moved over as the dog engagement in 4 gear was too shallow. This restricts the oil to the G4 bushes as I had to machine a recess in G6 to move it over.
With these holes drilled the lack of end float cannot cut off the oil supply but you still need some clearance.
Also do not use phosphor bronze bushes, only oilite.
 

greg brillus

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VOC Member
It is also very important to make sure the bush running clearances are not too tight. I have had cases of the bushes completely disintegrating turning the oil into liquid gold.
 

craig

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VOC Member
I am waiting for replacement C14 and wanted to plan my C19 shimming needs, seems I have quite a collection of C19 shims.
I wanted to see if this new set of parts , converting to latest Vincent spec, C3/2 and C20/1, is an expected clearance to begin to shim.
This clearance is 0.057" without a C19 shim and the nut is tight, but not torqued.
So 0.045" worth of shims might be required, is this common?
I am aware of other G3 shimming and this Rapide has 4000-5000 miles as is. Simply refreshing pieces that need attention.

25800
 


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