G: Gearbox (Twin) Twin Gear Change Adjustment

greg brillus

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A lot depends on how much use and /or abuse the machine has had. The G 49 and G 57 parts adjust how the G 66 AS lever assembly move up and down overall. These parts sometimes come loose on account of the 2 327 bolts coming loose for whatever reason, but the design is a bit weak, the small hex on the top of the G 57 tends to sink into the soft alloy of the G 49 and this makes adjustment difficult. The ratchet G 43 and the G 59 AS change speed pawl get wear on the teeth, thus limiting the amount of available travel. Even excessive play in the bush in the kick start cover can allow too much play at the G 66 lever. It does not take too much for the travel to suffer resulting in poor shifting. Having said all that, the parts do last an awful long time in service.
 

Ducdude

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It does not take too much for the travel to suffer resulting in poor shifting. Having said all that, the parts do last an awful long time in service.

I am not complaining about the durability of the parts only that wear needs to be considered if you are constantly having shifting issues as I have. A few new parts and we are back to going to fast and leaning over to far..!
 

timetraveller

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Regarding adjustability of the gear change mechanism, here is a photograph to frighten the children. I have been doing this to all my bikes for over fifty years. The original reason was not for access to the gear change mechanism. Older riders will remember a time then the kick starter springs use to fail at regular and frequent intervals. I remember, squatting in the gutter in heavy London traffic over fifty years ago trying to replace a broken kick starter spring. Despite the fact that some people will tell you they can do it without removing the exhaust system and the kick starter cover I could not. Hence, from then on, I have sawn off the top part of the kick starter cover, exactly as shown on the photograph on all the twins I have used on the road. The upper part is replaced for use on the road but this modification has never lead to any problems with gear change, ingress of water etc. Most people do not even notice it has been done but you will see from the picture how much easier it makes playing with the gear change mechanism, no need to remove the exhaust system etc. and, of course, replacing the kick starter spring. "Look on my works ye mighty, and despair."
 

John Cone

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Having fitted a new G61 and spending quite a while trying to get it right i have decided that the G59 must be worn. I came to this conclusion having removed the G61 and found that there is still not enough travel to move the G43 (which is new) though a whole gear. I will get this clarified next week when i send it to Maughans for them to compare it against a new one and if it is worn they can fit it to the G42/1 for me.
 

vibrac

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Here is a picture to frighten the children even more..... :eek:
1581772457285.png
 

stu spalding

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Older riders will remember a time then the kick starter springs use to fail at regular and frequent intervals.
I fitted a K/S spring, depressed the lever once and the lever stayed down. There wasn't even a hint of temper in the spring wire. Almost as bad as the cup/cone headrace set which had been correctly ground on all surfaces except the bearing tracks which were very roughly turned. Still, I suppose that, compared with some marques spares supply, we should be thankful for small mercies. Cheers, Stu.
 

doctired

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I confess I have been playing with these things for to long to contemplate. But I still find Richardson's instructions hard to follow,I honestly could not tell you after adjustment if that lever will work in all gears or not. Sometimes it does and I have even been able to smack smack smack as per the book up and down, and some times nothing is right, and worst of all is a perceived perfect action on the bench and then one gear is not always trustworthy on the road. Its not that I dont understand the mechanism and I know if a part is worn, Its just I find the difference between a good gearchange and a poor one can be an almost imperceptible adjustment. Having also worked on the Albion box I think I can see where the ideas came from.
If anyone has an understandable foolproof method with or without Gismos now is you chance to tell us.
Alternatively I rather fancy trying the modifications developed by Thomo (He of the Four valve Vincent).
I have a problem on both my twins with third selection. It goes partly in from second but perfectly from 4th... odd.
 

greg brillus

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Check for distortion of the G 50 plate if the footrest hanger is pulling it inward, The 2 E 80 nuts on the battery platform will need adjusting further outward to stop the g 50 plate from bending in. This can cause bad shifting where the symptom seems odd........Good luck.
 
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