spacers for plunger springs, what is their purpose?

[spanersc]

Hi All. I'm currently putting together the rear suspension on my fathers 1952 Star-Twin. In the parts listings, there are 2 spring spacers shown, part number 67-4131 plunger (top) spring lower collar and 67-4127 rebound spring bottom collar, these were not present when the bike was stripped. If you read the BSA service sheets it states 'if fitted' for these spacers, so my question is, when were these spacers fitted and what was there purpose? I can only assume they increase the spring rates a little, perhaps when the duel seat was specified? Hopefully someone will know the answer. Regards, Peter

[muskrat]

G'day Peter, I would assume it would be for side car work as you can get heavier springs for the front for that purpose.
Cheers

[duTch]

Hiya Peter,
                  I've been wondering the same thing, the only other thing I came up with is that they could be placed above the bottom springs, or below the top springs to change the ride height.....?maybe?
    While on the subject do you mind measuring your spring specs - lengths,diameters,  number of winds, I had some made to guesswork donkeys years ago, and they're way too stiff and dangerous to dismantle,almost warzone-like, and want to change them.
   If anybody is interested I found this 'spring rate calculator' http://www.pontiacracing.net/js_coil_spring_rate.htm
 There are others out there, but this seems easier to use.
                                                         from Dutch

[spanersc]

Hi Dutch. Have sent you a pm.  Regards, Peter

[Rex]

To resurrect an old thread, on stripping my bikes' plungers, "main spring bottom collar 67-4131" is missing from both units. Worth seeking out spares, turning a couple up on the lathe, or just accepting that BSA didn't fit them to all bikes, therefore they can't be essential?
Were they for altering the ride height, anyone know?

[duTch]

 Hiya Rex-  I guess jury still out at lunch    maybe I better double-check my PM's... sorry in advance spannerPete !

 I be back sometime after lunch     

[duTch]

  Ok- this part of the jury had an early lunch (3am)a bit before brekky, and have now done some research, (messages received and replied to at the time, but my sent mail not saved, so not relevant here).

 Maybe I didn't have access to a parts list at the time, but acquired same soon after, and have now revisited it.
 
 

... In the parts listings, there are 2 spring spacers shown, part number 67-4131 plunger (top) spring lower collar and 67-4127 rebound spring bottom collar, ......

  My findings in the parts lists for '49-'53 & '54-57 show NO part #67-4131, but the following are listed;

      5;   89-4257       Plunger Spring Top Collar      (On TOP of Spring)
    14    89-4258      Rebound Spring Bottom Collar   (UNDER BOTTOM of Spring)
   
** 19    67-4127      Rebound Spring Top Collar **

 Unless my eyes are deceiving me;    ** conflicting information;-
 

.....and 67-4127 rebound spring bottom collar......

 So I've just had a look at mine and put 'em in on TOP of the bottom (rebound) spring, still no evidence of #67-4131; seems to ride fairly nice 

 That's the best I can do for now, so let's hope the rest of the jury don't lunch too long 

 

[Rex]

That's what I intend to do too. These "spacers" are different diameters; one fits snugly in the rebound spring upper (I have this one) so the other goes in the main spring lower position (the one I don't have).
I'll just replace as found as the missing items don't seem to be essential.
Thanks.

[duTch]

 

....... These "spacers" are different diameters; one fits snugly in the rebound spring upper (I have this one) so the other goes in the main spring lower position (the one I don't have)........

     ....unless i'm on a different plane they should be the same diameter...oh, brainfart- you may mean different OD's ?

 Can't see it being wise to put one in the top and one in the bottom whether in the same side or one in each side , unless as I say ' I'm on a different plane ', but now definitely 

[Rex]

Maybe I should have used plurals; I meant one spacer at the top of each rebound spring.
So...main spring..one cup at the top and nothing at the bottom. Rebound spring....spacer at the top and cup at the bottom.
No-one would intentionally assemble plunger units asymmetrically...would they?

[duTch]

 

...No-one would intentionally assemble plunger units asymmetrically...would they?.....

 Well yeah that's kinda what I was hoping...sorry but I must be a bit O.C.Dyslexic or something...

[morris]

No-one would intentionally assemble plunger units asymmetrically...would they?

Oh yess... they do! The person that previously "restored" my plunger did just that.
I found an extra homemade spacer about a 1/4 in thick one side that was meant to "level" both wheel brackets. If left out, the wheel spindle wouldn't go in although spring lenghts all measured up right.
The real cause of them being out of level was just that the brackets were bent. It could easily be seen when holding a straight ruler against them. I think the bike must have carried a sidecar at some point in it's life, hence the bent brackets.
I ditched the extra spacer and bent the brackets straight again. All's well now.