Gearbox identification

[RogerSB]

Thanks to all. I find all your views and comments really interesting.


The BSA manufacturing years being from August to July could well point in the direction of the gearbox being a replacement and that was my first thought.  At the same time for my GF to have been delivered to the dealer from the factory so early in January, taking into consideration the Christmas and New year factory close down holidays in those days (probably a week at least), it definitely would have been assembled in 1959 - but what month or week before the end of the year must remain forever unknown.


Here are pictures of the components, with part numbers in the file names, of what I'm going to use so I end up with matching ends to the cables at the handlebar levers and with the correct end of the clutch cable at the gearbox (whether replacement or not). So there is a cable (with a BSA part no) to do exactly that job.


As for the front brake, the cable abutment lug on the back plate isn't the threaded type - so definitely the post 60 design for the later cable but there is a 42-8774 (1961 - 62) cable that will do the job nicely and being able to use a slide-in adjuster at the handlebar lever to match the clutch.

[duTch]

 Will be interesting if that Clutch cable is made for this purpose and goes straight on with the Adjuster-Style lever (Clamp Assembly 40-8539), without shortening the outer any (as I had to with one I bought by description- part # ?? / overall cable length a bit short )

 Be also good to know the cable lengths, mainly difference between inner and outer, which makes it easier to make/modify one for different handlebar.

 I cant find a part # for the gearbox cable adjuster, if anyone knows or comes across that could be handy....(?), but do have a part # for the lever adjuster (60-3586 Cable adjuster locknut, 'cam' type, slotted).

[JulianS]

I dont think BSA listed the gearbox end adjuster as a separate part, it was just part of a complete clutch cable. Unfortunately the cables offered now seem to have a hex adjuster rather than the nice, easy to use knurled figer adjusters. I make my own cables and always crop the fittings from old cables and reuse.

Photos show an orignal adjuster and the gearbox clutch cable lug used on bikes with GA7 frames.

[Greybeard]

....easy to use knurled figer adjusters. I make my own cables and always crop the fittings from old cables and reuse.

Hmm, that looks great. I wonder if I kept the old clutch cable when I changed mine  . It is a bit of a pain to get a tiny spanner in there!

[JulianS]

Some info on cable lengths from Romac 1966 catalogue - first photo - and Clarks catalogue from 1969 second.

The Romac does not define what it means by "approx length" but I suspect it is length of inner.

The last 2 photos are also from Romac catalogue. The number and letter code under column marked "Illus. PP4/5" in first photo is decoded in the last 2 photos to show the cable end fittings - for example the 1948/59 clutch cable is illustration 9B.

[Greybeard]

Course, as long as the outer can be curved around obstacles what matters in a cable is the amount of travel. If the assembled cable is 20 feet long it should still work as long as the outer vs inner length is correct.

[RogerSB]

My cables eventually arrived today, results are:-
Clutch cable 67-8681 fitted fine.  Outer is 48” and inner 53.3/4” (that’s measuring them). I've seen them advertised as 48” x 54”. With that extra 1/4” they would be perfect (but that’s repro parts for you).
As you can see g/box adjuster is screwed fully in but the handlebar lever has 1/16" free play after taking up some free play with the lever adjuster. I also took the cover off the g/box and could just feel a gnat’s whisker of clearance between ball bearing and end of push rod.  Cable will probably stretch with use and there’ll be plenty of adjustment to go. So I’m happy with that.
Front brake cable 42-8774 not so good. Cable had all the right bits but the inner was a touch too long for my liking. With the brake fully adjusted to give a feeling of confidence the slide-on adjuster’s thumb screw had to be screwed well in along the adjuster and after cable stretch there wouldn’t be much adjustment left – so I reverted to the original 42-8771 cable, which I had fitted new recently anyway.
What I should have done (but didn’t think of it at the time) was measure the 42-8771 cable when it was off (which is a perfect length) and the new 42-8774 cable to compare them because, according to sizes I've seen on adverts, they are both meant to be outer 33” inner 41” – but clearly not all of them are!
Yes, the important bit is inner in relationship to outer.
I suppose these days with all the parts that are affordable being reproductions Julian's method is the only way to ensure you get it dead right.
See photos taken today.

[chaterlea25]

Hi GB,

I know we keep going over this but the early 6 spring clutch, (that is on my Plungie) is fine.

The plunger and swing arm clutches (six spring) are totally different to each other and cannot be compared 


John

[duTch]

 Julian, those tables are probably useful if the bits are available...
 Roger it may be camera angle, but looks like you could probably tweak the pushrod internal-adjuster out a bit(so the arm is parallel to joint at half travel)...?

  This thread has my attention, because I have the same setup as Roger on my '52-'56 Plunger built with parts I like or work better, and the lever setup is one of this, but didn't realise it is a actual A10 arrangement I'd been supplied six years ago, until I had to 'replace' the lever due to a truck interlude, (I'd always thought lever setup to be a random aftermarket item).

So- I'll admit that until now I've never researched what part# my Clutch cable should be, mainly as I've generally made up my own from what bits I have, but in 2011, I did buy the new Clutch-cable previously mentioned (where I shortened the outer) by 'description' from this mob in Sydney via eBay; Was/is a nice enough cable, but just a bit short for my liking @ standard length 48" outer/~53" inner and with the nice adjuster in first Pic(red b-ground), second pic is adjuster I've had a long time, and on a 'home-made cable'.

http://trojanclassics.com/

 

Transaction detail from  > Trojan Classics< ;   CABLE, CLUTCH, BSA, WM20 + most models to 1959. New
Item Number 200541428236$19.90 AUD1$19.90 AUD

 (I thought it had a part #, but can't find evidence of it, and there's no M20 parts listing I can find that has the same #)

  Interestingly I had a look at Dragans who have useful  graphics;
 https://www.draganfly.co.uk/index.php/bsa/bsa/a710--b3133--c101112--m202133/category/993-pre-unit-a-group

  Not much help I guess, and the bottom line is that to have a cable that accommodates both adjusters, may need to be custom (+ ~ 1" inner).

 Also had a look on SrM site, but no cables to be found