Thanks Mark,
Appreciate the suggestions, and I think you're onto something. I think the pivots may need some freeing up, but don't know how successful that will be. The aren't obviously gunked up, but this bike has probably been sitting for decades. Maybe I need to soak it in Simple Green, or something?
The other issue is that I now see that I have the earlier generation Jubilee - my return spring is completely different from yours. Thought I'd heard or read that the later generation springs were "stronger" - but it just looks like a much better design.
Here's a few pics: http://www.flickr.com/
Thanks again,
Alex Moll Marysville (near Seattle), WA, USA
On Apr 17, 2010, at 6:16 PM, Mark Bulgier wrote:
>
> Alex Moll wrote:
>
>> It seems the return spring in the rear Jubilee has lost all tension.
>> It'll downshift to the larger cogs, no problem - but it won't upshift
>> to the smaller.
>
> It's pretty unusual for a spring to lose tension. Contrary to popular
> opinion, proper springs don't "go soft" from use -- ever. (Though a
> particular part may have missed its heat-treatment and gotten through
> quality-control in a very soft state, in that case it was soft from
> day
> one -- it didn't get that way later.) More likely the spring has been
> bent, or come unhooked at one end. Or most likely of all, the
> spring is
> fine but one or more of the pivots of the parallelogram have gotten
> tight. This can happen from crash damage or from road grit getting
> in.
>
> It's easy to check the pivots -- just unhook the spring from the lower
> attachment, which is exceptionally easy on the Jubilee, it can be done
> by hand without a tool. Now the parallelogram should move back and
> forth easily; ideally it should feel almost frictionless.
>
> Here's a picture of the spring:
> http://bulgier.net/
> and one of it being unhooked (or re-hooked, I don't remember), with
> nothing but fingers:
> http://bulgier.net/
>
> If there's not extra friction in the pivots and you really do just
> need
> the spring to be stronger, this can also be fixed almost instantly by
> hand -- just bend the spring. Grab the end you just unhooked at its
> lower attachment point and bend it up, towards the dropout. Trial and
> error will tell you how much to bend it -- bend a little at first,
> then
> hook the spring back under its peg and give it a try. You have to
> bend
> it enough beyond where it needs to be for it to permanently yield
> ("take
> a set"). You'll know if it yielded because it won't return to the
> same
> place when you let go.
>
> If it looks like extra friction in the pivots is the culprit, you
> could
> try flushing any gritty contaminants out with your favorite solvent,
> then oiling them. I doubt you'll be able to disassemble the pivots
> for
> proper cleaning, they're smashed together at the factory and not meant
> to be disassembled.
>
> Working the oil into the pivots can take a while. Work the
> parallelogram back and forth (with the spring unhooked), with an
> excess
> of oil on the pivots, until the oil has penetrated throughout. Though
> you'll never know for sure if the oil made it everywhere, hopefully
> you'll feel a reduction in friction.
>
> If they're tight due to crash damage, chances of fixing that are slim.
>
> Mark Bulgier
> Seattle, WA USA