Dodgy speedo.

 Can anyone think of a fault that would cause intermittent operation of a
speedo head? Its on a 76 Honda CB200 - magnet spins in close proximity to an
aluminium disk - definitely nothing electronic about it

Its not the cable, that had very slight damage to the outer so it was
slightly longer relative to the inner so I replaced it.

My problem is to eliminate any cause other than the drive gear, its not
mashed as I've seen happen on other bikes (Norton Commando) but it may be
worn, the surface of the teeth is slightly concave but I don't know if
that's normal, and the cable drive turns when the wheel is rotated.

Any help?

TIA.

 
The only time I've had an intermittent speedo problem[1] it was a worn
speedo drive - traced it by swapping out the cable then the drive from a
parts bike I had handy

If you don't have a parts bike you could try using a drill to turn the
cable while it's connected to the speedo, that would let you see if it's
the speedo drive that's playing up or if the problem is at the head.

Thinking about it, I'd use a cordless drill which had decent low speed
control - I've no idea how many rpm a speedo cable turns at and you
wouldn't want to ruin your speedo while trying to establish if the
speedo drive was the problem.

If it is the head I've no idea what your next step would be.

Bob

[1] seemed okay in town but would drop from 60 to 20ish before climbing
back up when holding a steady 70 on the motorway
--
Bob Scott

 

I probably have a drive gear or two in the mixed odds & ends box but there's
no telling which if any are the right pitch, secondly both driving and
driven gear are probably worn, so I'll be relying on full tooth height of a
new driving gear to compensate for wear on the driven gear if that's what
the problem is.

Last time I tried that it soon became obvious that the drill was turning the
speedo backwards (handy for "clocking" the odo) a bit easier nowadays as I
have a reversible cordless. So its knock the handle off an electricians
screwdriver to turn the slotted end of the cable or find a scrap cable with
a snapped inner I can cut to convenient length to drive the speedo head.

 
Perhaps an itsy-bitsy spider has crawled up your waterspout?

Oh, and I might as well say something nasty to Piggy before he turns
this into a 100 post thread.

Sod off, Piggy.

 

Does the odometer work perfectly? If it does, then the speedo is faulty.
If not, then it'll almost certainly be the drive gear in the wheel. But
if the cable inner is turning fine, then my money would be on a dying
speedo.


--
BMW K1100LT Ducati 750SS Honda CB400F SH50 Triumph Street Cripple
If you don't know what you're doing, don't do it. Workshop manual?
Buy one instead of asking where the free PDFs are
chateau dot murray at idnet dot com