Fault finding.

After you've spent an hour in the midday sun taking the whole top half
of the bike apart to get to the back of the clocks, and put it all back
together. Then found some pliars, wrapped them in a glove and actually
got the bottom end of the speedo drive out of the wheel hub, a 3 minute
job at best, I imagine that the following is not to be expected:

The ability to pull the last two inches of speedo cable inner out of the
outer revealing a slightly chewed looking end. I just wanted to ask
because I'm utterly clueless about speedo drive mechanics, but I assume
that cable from end to end is supposed to be one continuous unit, right?

At least it's not a costly fix if I'm right.

Ta.

 

Correct.

 

Yes. The cable is bust. You might be able to get just a new inner. In
the old days a decent bike shop would make one up for you. Otherwise
you need a complete cable.

 

Yup. Typically the inner bit is like a tightly-wound spring, with
the bit that fits into the speedo pressed into a square, rather than
round, section. The driven end, at the front wheel, is often a cylinder
with a slot cut into it, driven by a tab off a worm gear in the hub. The
inner drive should be a separate spare parts item.

These cables are subject to severe wear-and-tear as they turn and
flex. Frequent and copious oiling or greasing is required to prevent the
failure you've observed.

--
Ivan Reid, School of Engineering & Design, _____________ CMS Collaboration,
Brunel University. Ivan.Reid@[brunel.ac.uk|cern.ch] Room 40-1-B12, CERN
GSX600F, RG250WD "You Porsche. Me pass!" DoD #484 JKLO#003, 005
WP7# 3000 LC Unit #2368 (tinlc) UKMC#00009 BOTAFOT#16 UKRMMA#7 (Hon)
KotPT -- "for stupidity above and beyond the call of duty".

 

Looks exactly as you describe, except that both ends of the cable are
terminated in square section. How would one keep the thing lubricated? I
have to rip off half the front to get to the top end of the cable.

The top end was dry, the bottom end a bit more oily, but traces of
corrosion like paste in there too. Nice and manky.

New cable's ordered, it'll be nice to have two dials sweeping upwards
again :/

 

Regular maintenance, I'm afraid.

If you go the oil way, you need to disconnect the cable from the
speedo regularly[1], and allow several generous drops of oil to penetrate
down the gap between the inner and outer parts. To use grease, disconnect
at the wheel end and remove the inner cable; wipe off the old lubricant
with a cloth or paper towel, very generously smear it with grease
(a molybdenum sulfide grease is recommended) and replace the inner,
making sure it fits into place at both ends.

Good luck!

[1] No more than 6 months/10,000 km

--
Ivan Reid, School of Engineering & Design, _____________ CMS Collaboration,
Brunel University. Ivan.Reid@[brunel.ac.uk|cern.ch] Room 40-1-B12, CERN
GSX600F, RG250WD "You Porsche. Me pass!" DoD #484 JKLO#003, 005
WP7# 3000 LC Unit #2368 (tinlc) UKMC#00009 BOTAFOT#16 UKRMMA#7 (Hon)
KotPT -- "for stupidity above and beyond the call of duty".