Author Topic: s/a gearbox mainshaft movement SORTED  (Read 265 times)

Offline Rich

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s/a gearbox mainshaft movement SORTED
« on: 22.03. 2019 21:01 »
Having now stripped two gearboxes and replaced all the bushes and bearings on one tested it  and reassembled one to keep it complete, neither had any in and out movement on the mainshaft, I have just stripped down the gearbox of the 1960 Gold Flash I bought a couple of weeks ago as the previous owner informed me that the final drive bearing was the wrong spec as it tightened up when hot, the bearing was the correct one so I put it back together and the mainshaft moves in and out, checking the parts kist there are no shims on the maishaft, any ideas?

Online morris

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Re: s/a gearbox mainshaft movement
« Reply #1 on: 22.03. 2019 21:20 »
The play is taken up by the mainshaft nut, timing side. After thightening there must be 0 play
There should be a washer/shim between bearing and ratchet pinion bronze bush.
Could also be the bearing moving in the housing. Did you insert the bearing securing clip?
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Offline Rich

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Re: s/a gearbox mainshaft movement
« Reply #2 on: 23.03. 2019 08:21 »
Thanks Morris, yes the bearing is tight in the housing and the clip is in place, however not sure if I put the shim washer behind the kick start ratchet gear, I will check on this later and report back, log splitting this morning, (hydraulic splitter, getting to old to lift an axe higher than chest height)

Offline Rich

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Re: s/a gearbox mainshaft movement
« Reply #3 on: 23.03. 2019 17:59 »
Well who's a daft twit, I went into the workshop this afternoon to have a second look at the gearbox and what was staring at me in the box where I put all the bits? A shim washer that should have been fitted behind the kickstart ratchet gear, fitted it and now everything is rosy, I became a bit complacent, easy to do, but just as easy to rectify, so long as you notice any faults, Thanks Morris

Online duTch

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Re: s/a gearbox mainshaft movement NOW SORTED
« Reply #4 on: 24.03. 2019 04:53 »

 Another *very* important bit that can be overlooked is the thrust washer between the 'F' and 'H' gears on the layshaft, and fitting it so the chamfer is toward the spline....
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Offline Swarfcut

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Re: s/a gearbox mainshaft movement NOW SORTED
« Reply #5 on: 24.03. 2019 08:39 »
duTch.. A timely reminder there about the chamfer.
      This washer is hardened, and depending on the  flange thickness of new layshaft bushes, the layshaft and first gear may bind as the inner case is tightened down. It is easier to relieve material from the face of the open layshaft bush. Too much layshaft end float needs a new, thicker washer. Here I would have thought a brass washer would be fine, as a bearing surface, since it is not under any great load. BSA must have had their reasons for specifying a hardened steel washer.

 Any thoughts?

 Swarfy.

Offline Rich

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Re: s/a gearbox mainshaft movement NOW SORTED
« Reply #6 on: 24.03. 2019 09:31 »
I will need to take the box apart again to check the layshaft shim for correct fitting, also from what the previous owner told me about the drive side bearing being the wrong spec as it got tight when it was hot, which upon investigation it was the correct one, but reading the posts I came upon one which talked about the two bushes fitted in the mainshaft 4th gear, and there should be a gap between them for oil, well I did not check this, or if oil holes had been drilled through, the bushes have been replaced, so maybe that was the reason things got tight when hot.
I will report back later

Offline berger

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swarfy its hardened because it fits between the gears and not up to the bush with the chamfer against the shaft splines, a hardened steel washer fits up to the needle roller in the sandwich plate on a rrt2 edit and from what I have read over the years up to 20thou float is ok

Offline Swarfcut

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bergs, Yes you are right, it does go between the big first gear and the 19 tooth layshaft sliding gear. Thinking about it, it must be tough enough to resist the grinding action of the end of the layshaft splines, even though it is not under any great loading. So although brass would be a better bearing material in the short term, the soft metal would not be any good for long term reliability. But brass or mild steel would be good enough to get a bike on the road while searching for the elusive correct washer.

 The chamfer is to clear the face radius change in shaft diameter at the start of the splines.

 Swarfy.

Offline Rich

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the gearbox is now back together, the shim between the gears on the layshaft is the correct way around and the 4th sleeve gear on the mainshaft had the two bushes butted up against each other, so I put it on the lathe and with an internal cutter machined a gap between them, this should help stop the mainshaft from tightening up. If this is the wrong thing to have done, I don't care it is not being taken apart again!!!!

Offline berger

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Re: s/a gearbox mainshaft movement SORTED
« Reply #10 on: 24.03. 2019 19:49 »
rich there should be two bushes anyway , one each end of the gear so maybe it has had two long bushes fitted or one long one *dunno2* so a gap in the middle is correct