speedo trouble

[3BeanCrispy]

so i'm out riding my ca77 last night, had it up to almost 60 mph which is the fastest i've had it going ( just been puttering around town). I start to hear a whining sound from the front end. I stop and check things out, and everything seems ok - nothing seemed sloppy or hot, nothing smoking, so i shoot back down the road again. the whining persists, and the speedo needle was bouncing about over a 15mph range or so. i stopped by the house, popped out the headlight, and disconnected the speedo cable from the speedo and the whining ceased. I'm figuring the speedo internals went kablooey ? i havent read on here of anyone having much luck/experience taking them apart and fixing them. i do recall reading somewhere about a place that may be able to fix them.
anyone else have a speedo poop out similarly? thanks in advance!

[mike69]

You could try and soak in about 2 inches of penetrating oil. I've taken several apart that were frozen and brought them back to life. It takes a lot of patience but it can be done.

[Erich]

Have you pulled the inner part of the cable out? It sounds like you may have broken it.

[3BeanCrispy]

have tried nothing yet, thanks for the ideas! i'll definately look into them both this weekend.

[e3steve]

so i'm out riding my ca77 last night, had it up to almost 60 mph which is the fastest i've had it going ( just been puttering around town). I start to hear a whining sound from the front end. I stop and check things out, and everything seems ok - nothing seemed sloppy or hot, nothing smoking, so i shoot back down the road again. the whining persists, and the speedo needle was bouncing about over a 15mph range or so. i stopped by the house, popped out the headlight, and disconnected the speedo cable from the speedo and the whining ceased. I'm figuring the speedo internals went kablooey ? i havent read on here of anyone having much luck/experience taking them apart and fixing them. i do recall reading somewhere about a place that may be able to fix them.
anyone else have a speedo poop out similarly? thanks in advance!

I've no experience of CAs, but I do understand speedos (signs of a mis-spent past!); the input shaft (the squared female part where the cable inserts) is a (usually brass) rod that ends up at a magnetic 'rotor'. The rotor -- a type of flywheel -- spins inside a metal 'cup'; said cup is attached to a tiny brass shaft upon which the needle is mounted. This shaft is usually lightly oil-damped, thus eliminating needle waver & bounce, and is restrained by a hairspring. The tension exerted upon the hairspring is adjustable (by experts only!!) and it is this tension that calibrates the needle's excursion and, thus, the needle's position at the various rotational speeds of the speedo drive>cable>input shaft.

Your whine is possibly a result of the rotor touching the cup (has the instrument been dropped or jarred?), but probably just a dry input shaft, which would explain the needle's waggle, as the shaft cannot spin freely enough to provide linearity.

Ride the bike for a short distance -- say a mile or so -- with the speedo connected, then remove the headlamp and feel if the cable's thumb nut is getting warm. Remember that it's brass inside aluminium alloy, so don't let it get too hot.