spacers

[RDfella]

Plunger gearbox. All the mounting holes to engine and the top rear mount were so oversize and un-round that I had to get them welded up. Just finished machining / re-boring holes and now ready to re-assemble.
But - the laygear shows two spacers. One is 67-3101, layshaft gear locating ring, and t'other is 67-3203, layshaft thrust washer. Trouble is, they're both the same size, save for thickness.
Anyone know which one goes where? Did BSA have a washer dimension chart?

[JulianS]

67 3101 is the wire circlip which fits on the layshaft to locate the fixed (the "B") pinion.

[JulianS]

Of the 2 67 3203 thrust washers I have one is 87 thou thick the other 93 thou thick The bore has a chamfer to clear to the fillet on the layshaft .

[RDfella]

Think I'm sorted now. I found Draganfly's diagram wasn't, unusually, much help this time. The S/A BSA leaflet proved better, albeit with a different gear change mechanism. As Swarfy said, I was getting confused by the snap ring retaining the gear. Semantics, I suppose.
As far as I can see now, there's no thrust washer on the laygear's end, but one between the two last gears. Presumably this washer was available in different thicknesses to adjust end play.

[berger]

RD the smaller fixed end gear runs against the bush . the hardened washer sits against the shaft with the chamfer relief bit to the splines and the straight face to the first gear that also runs against the bush.

[Swarfcut]

  Correct RD. My take is that the circlip provided a positive stop to locate the laygear pinion position on the shaft in production.

  With more time in the comfort of your own workshop, the pinion can be moved back towards the shaft end to give the running float required. They are usually a very tight fit, but can be adjusted with precision smacks. The face of the pinion is always proud of the shaft spline end faces, pinion face runs against the blind bush, berg's note.

  Cheat's method, all a bit simpler than searching for hardened steel thrust washers in varying thicknesses, one of which to hand must be used to maintain a basic layshaft endfloat setting.

 Swarfy.

[RDfella]

Just a quick check here.
Gears assembled, selector plate in neutral. Remembering this is a plunger box, is there any specific position the selector should be in where it mates with the cam plate? On s/a boxes dots must be lined up (or un-lined, as I discovered on my GF) but that is a different mechanism. Reason I ask is because gears don't select (without the outside casting fitted).

[Swarfcut]

  Try it fully assembled, could be it needs a bit more leverage.  Both boxes are assembled  in neutral with camplate plunger on  smallest (neutral) dip.  Plunger gear selector arm is not always in the same relative position to the camplate as on the "geared" S/A design, and in practice is aligned for assembly by the two return springs in the outer cover. So in neutral, ball arm horizontal, outer cover on.

   Gasket thickness can be critical according to earlier posts, as is the plunger spring tension and the ease of movement of the plunger tip against the camplate edge. The camplate moves under the plunger force ready to pick up the next claw movement, less so on the S/A box with a more positive linkage.

  Also check camplate movement is not restricted by selector arms' pips binding in camplate tracks, too thick a camplate (factory second?) or bowed selector shaft.

 Swarfy.