G: Gearbox (Twin) New Gearbox: Help Needed

greg brillus

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I've seen pictures of it all.........Yes it has an external sprung index and roller on the outside of the kickstart cover that runs directly on the G 40 shaft, and replaces the camplate plunger for a sprung roller with much larger detents in the camplate. The second part looks quite easy to do.
 

highbury731

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G61/1 has tabs on it to prevent over-selection. I bought one, and had to bend both tabs back to get enough travel to engage gears. I have heard of people making their own version with adjustment screws to set the limit stops where they want them. I may have to do that myself.
Paul
 

vibrac

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Yes I have done this on the twin racer by brazing 1/4 bsf nuts on edge and using cap heads for adjustment the kick start spring prevents this on a standard bike but racers and people who have confidence in the electric start could use it
 

BigEd

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G61/1 has tabs on it to prevent over-selection. I bought one, and had to bend both tabs back to get enough travel to engage gears. I have heard of people making their own version with adjustment screws to set the limit stops where they want them. I may have to do that myself.
Paul
The G6/1 can improve the gear change but due to the mix/match of components, they need some tweaking to have an effect. The standard G6/1 is quite flimsy. I made my own with two nuts for adjustment and some bracing to stop the nuts being bent backwards. A problem with this mod is that there is not much space here and the nut closest to the timing cover is fouled by the kick start mechanism. I have space as I have an electric start and the kick start mechanism removed.
This mod is only a partial solution as the G61/1 only limits the movement of the G59/AS. The rest of the mechanism inboard can carry on turning due to the momentum of the camplate etc. This is probably not so much of a factor for normal gear changing but more of a problem when going for a fast change or people who are used to stamping through the gears on more modern gear boxes..
Phil Irving proposed a fix by welding and filing to make a revised G43 that acts like more of a gear to keep it locked to the corresponding part on the G59/AS and so preventing the G40 shaft continuing to turn due to momentum. This is easier to understand with an M003 parts drawing to hand.;) I think you may find it described fully in 40 Years On. I have not tried this yet, maybe sometime.
 

timetraveller

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I get the G43s made and supply them to the Spares Company. Years ago I saw a drawing by Phil Irving in which he drew up a modification which resulted in 'square' teeth rather than the triangular ones. That is probably the same one that BigEd refers to. I have never been able to find this drawing again. My memory is that the part of G59AS which meshes with G43 would also have to be modified. If there was sufficient interest, and someone can find the drawing, then I would be prepared to investigate getting a batch made. Over to you.
 

Gene Nehring

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A few years ago John showed me the AMC style camplate he had made and fitted to the 4 spd in his Shadow. At that point in time he had removed the 4 speed and installed a Quaife 5 speed in the bike. According to John, the 4 speed with his revised plate shifted as well as the Quaife, which is a slick shifting setup.

I'm guessing that the 4 speed gear set and special camplate are put aside as part of the Black Shadow, which his family has kept.

Glen

Glen,

The whole gearbox and cam plate are part of the engine I purchased from the estate. We had some issues trying to fit the gearbox into the cases yesterday. The alignment of the bearings on the main shaft is out.

It was a G2 issue that is now resolved.

So I have the cam plate and could post a photo.
 
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