A10 S/A Yokes on Plunger A10

[MidlandsA10]

Hello all

I am slowly assembling my “box of bits” Plunger A10.

I have a cowpat headlamp to fit.  When I assemble the yoke (on roller bearings) the fork shrouds are half an inch shy of touching the top yoke, and the headlamp shroud is a quarter of an inch from the bolts lining up.

The yoke is from an S/A A10 (67-5028).

Does it need to be a Plunger yoke, or will the gap reduce when I install the forks on the taper?

It may be worth noting I have tapered roller bearings fitted, but I removed the champer as required.

Best wishes

Tom

[CheeserBeezer]

Hi. It shouldn't matter which yokes you use. It is well known that the taper bearing kit extends the distance between the top and bottom yoke, but only slightly, maybe 2 or 3 mm. This might account for the misalignment of the headlamp shroud. The big gap between the fork shrouds and the top yoke suggests you might have the wrong fork shrouds. I'd assemble the the yokes onto the frame properly and fit the fork legs properly before making any further assumptions. Once you've done that you can post some pictures and measurements which forum members can compare with. A starting point might be to check you have the correct fork shrouds. Suggest, measure overall length and measure from top to bottom yoke pinch bolt hole.

[Swarfcut]

 Not as simple as it seems, there are multiple choices here.

  Lower yokes are different, Plunger has the steering stop as part of the forging which abuts the frame stop on full lock. S/A type uses a bolt on damper anchor plate to do the job.

 Top yokes all use the same basic dimensions for stanchion taper and steering stem. The differences are some have smooth tops (early) later have a couple of pips on the front edge, later still have a hole for the steering lock, and the distance apart of the legs differs according to the model range....looks right but won't fit. Also the possibility that the trail angle may differ depending on the yokes used.

 Top yokes...66 5088   Early type up to 1953 Rigid and Plunger

                  65 5430  '53   for Plunger with no steering lock, the introduction of Cowpat Cowl.

                 65 5448   '54  onwards,  Plunger,  no steering lock according to parts list reprint 1958
               
                42 5035    '54 S/A     no steering lock

                42 5036     Road Rocket, pips at front which may be tapped for tacho mounting plate, provision for steering lock.

 All from my catalogues to hand, but other variants may exist. Drags' online parts listings show even more that may be encountered, and the same pictures for different part numbers to add more confusion.

 The identical forging may be used for different model variants, machined and treated differently, so the forging number may not match the actual part number.  67 5028 as such does not appear in my A7/A10 parts books, but from Drags catalogue and an ebay listing looks to be plain top early type, no pips, used on Rigid bikes 1947/48. Fork shrouds are the same for Plunger and S/A, so with the correct BSA Parts the problem must be the bearings as CB relates.

 Swarfy.