The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Gearbox, Clutch, Primary => Topic started by: Seabee on 05.01. 2021 23:08
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Hi all,
I couldn't find much on a search, although I know it's been talked about over the years. I am in a somewhat common situation I suspect, where my layshaft is worn to a point that new bushes will not take up enough clearance. I do have the ability to make my own bushes, but thought maybe a roller conversion would be a great long term fix? What all is involved besides the obvious over-boring of the case and mid-plate? I would have to come up with thrust washers and figure a way to fix them in place I would imagine, and get the layshaft ground down to the proper diameter and surface hardened?. Just looking for some advice from experience.....
Seabee
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You will need a needle roller layshaft & machine a recess in the main casing to suit a thrust washer next to the 4th layshaft gear.
As per s/c tt style boxes. For a quick & reliable fix, have the worn bearing surfaces ground true & make bushes to suit. This subject has been discussed recently maybe a quick search will find it.
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The needle roller layshaft does not have an oil scroll on the clutch side end.
The blind needle roller fits in the same hole as the blind bush, the flange of the bush and the thickness of the thrust washer are nominally the same at about 0.11 inch, and the outside diameter of the bush is slightly greater than that of the thrust washer so usually no machining needed to the case there. If you want the core plug on the outside you need to machine a shallow recess.
The thrust washers, different at each end of the layshaft, are straight from the Goldie parts list. They are not fixed in position, just slip on the shaft between the pinions and the case and inner cover.
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Thanks Julian. So the big deal is getting a roller bearing layshaft to start with! The rest seems entirely doable............