Hello!
My gearbox is clunky after rebuild, and I suspect the reason could be either lack of, or wrong placement of, thrust washers. My parts book show just one: 67-3203 placed between first and second layshaft pinion as seen from the selector/timing side. But a search on this site revealed this quote:
According to the late John Gardner, Tech Officer of the GSOC UK, "There are four large hardened washers . . . , three on the layshaft and one behind the kickstart ratchet pinion bush . . .Unfortunately, the BSA Spares List illustration [Plate 5, A Group Plunger] does not show clearly the correct assembly.
Working from the clutch end of the gearbox, the washers should be assembled on the layshaft in the following positions.
Part number 42-3078 is fitted between the main gearbox shell and the layshaft fixed gear 'B'.
Part number 67-3203 is fitted between the 'F' and 'H' gears.
Part number 42-3079 is fitted between the 'H' gear and the middle cover.
Part number 67-3161 is fitted behind the kickstart ratchet pinion bush."
The "Layshaft Thrust Washer", p/n 67-3203, located between the 'F' and 'H' gears, has the following dimensions;
.093" (.115 ") thickness*;
1.093" (1.248") O.D*.;
3/4" I.D.
*The difference between the two numbers show the practical tolerance that I've experienced. The first number is John Gardner's, the other is what I have in my A-10 and/or Gold Star boxes.
John goes on to say "Pay particular attention to the washer part number 67-3203 which is also used on the gearboxes fitted with bronze layshaft bushes. The bore of the washer often . . . has a chamfer on one side only. If this is the case, the washer must go onto the layshaft with the chamfer against the spline, to give clearance for the small radius on the shaft at the start of the spline."
Now, can anyone shed more light on this? Should there only be one correct number of washers? I have only one in my box, and have had good clean shifting with this before the rebuild. I might have messed it up, or maybe the closer tolerances have played havoc with old forgiving slack?