Top Fork Yoke

[Russ]

Can a someone please confirm the Part Number for the Top Yoke and Bottom yoke for a 1951, A10 Plunger. Also the measurement across the centres.
I have just found that I have the wrong top yoke, but can't see the part number on the bottom. Fortunately I am still in the preparation stage so will be able to fix problem before it is too late. I have checked the net and Draganfly etc but only found the number for 1953 A10 Plunger which is 65-5430.
Thanks Russ.

[Swarfcut]

  Measured on S/A and Plunger lower yokes to hand it's 6 3/4"between leg centres.

 From my Parts Books....

 '49/53 Parts list shows top yoke as 66 5088 used up to 1953. 65 5430 used next, then another change in 1954 to 65 5448. Later Plunger bikes have a steering lock, I do not have that list or reference, but yoke 65 5448 to hand has the lock.

 Bottom yoke listed as 66 5089 for '49-53, and continues to the end of the Plunger Frame.

 Dimensionally all variants will be the same with regard to threads, bearings etc. Minor changes eg threads for ancillary brackets, smoothed off lugs etc could be the reason for differing part numbers. I would expect the fork geometry to stay the same, but who knows?

 Top yokes generally have a casting number. Lower yokes are all unmarked in my examples. A good bet that any post 1950 A Series lower yoke with the correct form of steering stop will do the job. Drags are worth a look, but sometimes may add to the conundrum.

  Swarfy.

 Additional. I have a top yoke with forging number 65 5398....looks to have original factory Golden Flash Beige enamel. This does not appear in Drag's list for A,B,M ranges. Casting and forging numbers are usually close to the part number, but not always the case. Plenty of top yokes on ebay this week, some made of gold. Sellers often don't know what's what, but useful as a guide.

[limeyrob]

What do you mean by "wrong"?  So long as the stanchion centres are correct and the spigot bore then it should fit.  There are various tapped holes for instruments and cowls that vary but the forgings (or casting?) seem to be mostly the same.  I've recently added some tapped holes in my top yoke to adapt it.
Its also an easy part to swap later so don't hold up the whole build, the correct one will turn up on e-bay or at an autojumble.

[JulianS]

Some photos might help?

The black bottom yoke is swinging arm the other plunger.

[Russ]

Thanks guys for your replies. The measurements and photos are a great help. It looks like I have the correct Bottom Yoke.
My "Wrong" top yoke is part number 65-5365 which appears to be for "B" Group 47 to 48.
Now my story as to how we got to this point. My 51, A10 Plunger is assembled, minus complete engine, and painted in etched primer. I have been "restoring" it for 15 years. Yes you read that correctly. Today in a conversation with a mate, who is a BSA expert, he mentioned the taper in the top yoke where the fork stanchion fits. I said mine has a step in it. Oh something is wrong. I checked mine and found that it is the wrong part which has been modified by a previous owner.
Now to the untrained eye, mine, it appeared normal and as it should, so for the past 15 years I was none the wiser.
As I always say, the advantage of taking soooooo long is that I will find everything that needs fixing before its too late.
Thanks again guys,
Cheers Russ

[Worty]

15 years Russ  

[limeyrob]

OK a step sounds bad news.  Looks like you need a replacement regardless if your stanchions are taper.  Top yokes seem to last and don't fetch much money so I don't think its a show stopper.

[berger]

Russ when you get the correct tapered top yoke bolt everything up and check for fork twist, i know from personal experience if the top yoke has been damaged [ in a crash or a bad spill ] it will tend to pull and twist the forks when they are fully tightened in the tapers.

[MikPowl]

Firstly, my resto is 40 years in, and I still haven't reached anywhere as far along as you have - well done!!  About the top yokes - I think that the other comments are exactly right - use any of the items that you mentioned - the only issue might be drilling the bosses for attaching an instrument plate. The main differences between the early and later yokes seems to be (a) the early yokes have a narrower spacing between the handlebar mounting risers than the later items and (b) the yokes seem chunkier and more 'shaped', particularly around the stanchion mounts. The very early 66-5088 yoke has the instrument mounts - it was changed in '53 for the Golden Flash (no instrument mounting) but retained for the Super Flash which has an instrument carrying plate mounted on the yoke.  Again changed in '54 to the chunkier variety mentioned above which is also fitted to the later S/F like mine. Just a bit of useless info....

[limeyrob]

Its worth putting the stanchions in the bottom yoke and clamping them up then seeing how they line up with the top yoke.  Its possible for a prang to twist the bottom yoke crossways.  The top yoke just rotates on the spindle so its straight. This can take a while to work out.  This also checks the centres are correct.  You can do this on a bench with the fork stanchions flat face down so you know there's no twist.
When I built my A10 up a month or 2 ago I put the forks on the bare frame and I found it easier to do that with it all upside down then flip it over to put the box and engine in.

[Russ]

Yes I will replace the yoke with a correct, unmolested, one. As suggested I will bolt up the stanchions and check alignment.
Yep Worty, 15 years but I feel much better now that MikPowl has taken 40 years.
Thanks for your help,
Cheers Russ

[Jules]

I agree with you Berger, my (basket case) bike had bent yokes and forks but I didn't realise about the yokes until I tried assembling the straightened legs - the problem will be be finding "good" yokes, if I put my old ones on Ebay you wouldn't know until you tried assembling everything!
At the time I picked up a pair of good yokes from the forum which were for late plunger, so I've had to modify the stop arrangement to suit the s/a model.....

[berger]

i went out Oout yes to the pub  , i had my stuff stoved then found out. so took the whole lot to work and benched it  then had to weld 3  3/8ths whit studs onto a 1inch plate then put good owd made in england thick spreader washers onto the top yoke and get it hotter than Mc hot and pull the nuts down on the studs and watch it say thankyou when it's cooled down. the downside was the black stove was toast so i got some red instead or is it orange ? don't know i'm stupid as well as colour blind  but the upside is i can let go of the bars and she behaves very well if i built her with the black stove on and took my hands off i would be toast. thankyou for listening have a nice day .