Author Topic: RGS fork yolks  (Read 122 times)

Offline Sunbeam

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RGS fork yolks
« on: 13.09. 2019 14:41 »
Could anyone please help in identifying what  should be the correct yolks on a RGS, apologising in advance if this topic has been covered in the past. During the rebuild of my forks I had to remove both upper and lower yolks and found that the bottom yolk tube had been badly damaged in fitting the bearing cup. Checking the BSA part list numbers has totally confused me. There is no number on my bottom yolk and the steering stop isn't drilled to accept small set screws, I believe it should be as the gold star. There is a large dimple where the  steering lock is fitted to some models and 2 small tapped holes I believe we're for the provision of a horn again fitted to other models. From the parts list the bottom yolk should be 42-5015, top yolk 42-5011...my top yolk is 65-5398 which I think may be from an A50 or A65 but not sure if BSA were just fitting parts what were available when my bike was built in 1962. I really would appreciate any help in sorting this out as to whether I should search for replacement parts.....Howard
Howard

Offline Swarfcut

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Re: RGS fork yolks
« Reply #1 on: 13.09. 2019 16:43 »
Howard... May I suggest the Draganfly online parts catalogue to supplement your own parts book. This will enable you to compare the part numbers of what you have and what you should have.
  Yokes are a minefield, sometimes having forging numbers, sometimes not. In addition, some basically identical forgings will be machined differently, threaded holes added etc, and thus have different part numbers, although still carrying the same forging number, which can be different from the part number by a fair amount.
  As a general rule for the major castings, the part number differs from the casting number by one or two digits, but there are exceptions, as here.  Slim chance you can  identify your existing parts as being correct or spurious without comparison to a known correct item, so hopefully other Forum Members will be able to help.

Swarfy

Offline Sunbeam

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Re: RGS fork yolks
« Reply #2 on: 13.09. 2019 19:57 »
Thanks very much Swafy, I will download the Dragonfly catalogue to compare part numbers, the BSA and Bruce Main Smith spares lists are confusing as they give part number 42-5011 for the top yolk, (then in brackets states use 42-5036). I've spent a fortune over the years trying to put right what a dealer did or didn't do before I bought my RGS. The forks were the latest episode buying new stanchions, spring and bearing kit, having previously purchased a replacement 190mm hub as the existing one had been butchered around the bearing locking rings. I may try Vale Onslow to see what they come up with as they do hold new old stock parts, thanks again... Howard.
Howard

Online morris

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Re: RGS fork yolks
« Reply #3 on: 13.09. 2019 22:04 »
And to add to the confusion, my 1960 parts list shows two part numbers for the top and two for the bottom yokes. One of each is marked export
For as far as I know, the top yoke tapped holes are fore fixing a speedo and tacho so should be ok for an RGS?
Bottom yoke 42 5086 has a fixing hole for the horn and the drawing shows two nuts that apparently go nowhere unless they go on two set screws, but they’re not on the drawing.  *conf2*
Edit; All right, it’s the pinch bolt nuts, silly boy...
But there seem to be two threaded holes at the steering stops for a set screw?
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Offline trevinoz

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Re: RGS fork yolks
« Reply #4 on: 14.09. 2019 01:30 »
Howard, It seems that the bottom yoke is from 1958 on for models with a nacelle, the horn is mounted on the small tapped holes.

I have a feeling that your top yoke comes from a plunger model.
Top yoke should be 42-5011 which has no steering lock but does have two tapped holes for a speedo bracket which, on the RGS, have domed set screws fitted to plug the holes.
The top yoke was used on 1954 A & B models also as well as Gold Stars. Number cast in is 42-5010-1
The bottom yoke should have a number cast into it, mine looks like 42-5013 or 5015. There is an undrilled dimple and is drilled and tapped for the steering stop.
You will see $20.00 written on the top yoke. That is what I paid for the set at a swap meet a couple of years ago. I couldn't believe my eyes when I saw them.

Offline Sunbeam

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Re: RGS fork yolks
« Reply #5 on: 14.09. 2019 12:07 »
Thanks Morris and Trev for your your replies, things seem to be getting clearer now what I have on my forks and I'll look out for the correct parts, looks like by the time I've finished I will have changed the entire front end of my RGS. I've attached some pictures of the top and bottom yolks (no casting number or drilled fork stop screws) ...many thanks.... Howard.
Howard

Offline Sunbeam

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Re: RGS fork yolks
« Reply #6 on: 14.09. 2019 12:19 »
More photos of my top and bottom yolks... thanks... Howard.
Howard