A10 BSA crank main bush size spec

[Richard Hinton]

Hi Guys

Had crank ground, main bush is ground to worksheet 207 details the company informs me that its -20.
I have bought a -20 bush and its too big, they have the crank back to confirm what size they have ground it too.
But in the meantime does anyone know based on the work sheet 207 spec details, what this size actually is -20. -30 -40?

Is the bush wrong or the they have over ground it? I may be able to exchange the bush but need independent verification. If you can help look forward to your reply. Richard Hinton

[CheeserBeezer]

My data shows std timing side bush is 1.375", so 1st cut on the crank would be -.010" = 1.365" then allow about 0.0005" ~ 0.001 clearance so crank should be 1.3645 ideally (no less than 1.364"), then -.020" crank should be 1.3545"..... according to my data and my mental arithmetic. No responsibility for getting it wrong etc.!!

[chaterlea25]

Hi Richard
The bush will not work from the box, they need the bore to be smaller than the crank.
After fitting the bush has to be line bored or reamed from the drive side bearing to give the running fit to the shaft size

John