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Layshaft bush positioning

The layshaft bush and forkshaft bush on the driveside both have a groove, does anyone knows if they have to be positioned or can they pushed in at random. ??

Regards, Michiel

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email (option): m.wijbenga@hotmail.com

Re: Layshaft bush positioning

Hi Michiel...A good point and something I have often wondered about. In all my BSA literature there are no specific instructions regarding this.
Both bushes are splash fed by oil thrown up as the gear cluster turns and in whichever position the slot is located it is hard to see how that would assist lubrication...though when positioned at the bottom or to one side this might allow oil running down the face of the bush to 'migrate' along its length.
As the slot is cut to the end of the bush the slots would not work as an oil 'resevoir' when the box is stationary either.
I tend to go with fitting it to one side...it is possible some oil might then 'sit' in the slot...but I might be wrong!..
...Ian

email (option): ian@wright52.plus.com

Re: Layshaft bush positioning

Hi Ian, I just noticed the bush in a pre-war housing does not have the slot, so it looks like a later modification.

Could it be that the slot is cut in to get a larger circulation of oil going? And that the slot is only meant to act as the return ? The spiral groove which is cut in the layshaft will pump oil into the blind bush but if it has no return the pressure behind the shaft increases and oil circulation is less than with the slot ??

As for the 'oil-reservoir', when the slot is not at the bottom, the oil behind the end of the shaft can not run out, so there will be a small reservoir of oil behind the shaft. But maybe than the dirt in the oil will also collect there. Until the bush is worn out of course, which mine are most of the time

Regards, Michiel

email (option): m.wijbenga@hotmail.com

Re: Layshaft bush positioning

Hi Michael, The problem with the circulation theory is that the selector shaft does not rotate and doesn't have a scroll...but does have the slot..Ian

email (option): ian@wright52.plus.com

Re: Layshaft bush positioning

Hi Ian, Yes that is true, but this shaft can almost do without oil at all I should think.

I still believe in the 'circulation theory' : the other side of the layshaft is also blind and does not have the slot but here the oil is forced back through the center of the shaft to the gears.

Anyway, if the position of the slot is very important they would have designed it in a way it couldn't go wrong. I think I will just close my eyes and put them back...

Thanks, Michiel

email (option): m.wijbenga@hotmail.com

Re: Layshaft bush positioning

Hi Michiel, It's the same with the oil hole in the intermediate gear spindle in the engine...position is not specified...As that is fed with oil mist through the crankcase wall into the back of the spindle having the hole at the bottom would seem to be the logical way...The bush there does tend to wear quite rapidly...I think it should probably have had a positive feed like the cam spindles..Ian

email (option): ian@wright52.plus.com

Re: Layshaft bush positioning

another thing i couldnt find out which way was the oil flinger on the crankshaft i put the new one in the same way that the one that come out yes ian i will get my b31 going one day

email (option): roger.back@node6.com

Re: Layshaft bush positioning

Just noticed the earlier engines, like the Sloper, has about the same design of intermediate gear spindle, also with the hole in the crankcase for the oil mist fed, but there is no bronze bush, just steel on steel. I did not notice a large amount of wear of this gear in the few crankcases I had in hands...

Also the cams are without bronze bushes and run direct on the fixed spindles. Wonder why BSA choose to add the bronze bushes ??

Regards, Michiel

email (option): m.wijbenga@hotmail.com

Re: Layshaft bush positioning

Hi Michiel...Everything wears eventually I suppose and introducing a bush makes a 'service repair' possible. Also it frees up the tolerances at the production stage for the gear bore and/or spindle diameter..these do not have to be made so accurately if a bush is used and sized to suit after fitting. I guess scrap bushes are cheaper than scrap gears if outside of tolerance..Ian

email (option): ian@wright52.plus.com

Re: Layshaft bush positioning

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email (option): unpob@yahoo.com

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