Dodgy Rev Counter 500 4

[paulbaker1954]

Could use some advice!!

Rev counter climbs lovely to 5k then sticks  there and then jumps to 8k or thereabouts.

I have new cable, squirted some WD up the hole etc and still no better.

I am kind of coming to the conclusion that the P.O. rode around a lot just under or around 5k and it’s developed a “sticky point”

I have 3 alternatives

1) Send it for repair ( but that does look very expensive from the research I have done.

2) Source a fleabay replacement (not much around) and may be just as bad.

4) Have a bash at stripping it myself and seeing what I can do.

So now to my question, has anyone got any experience of repairing these units. I think they use a magnetic rotor system so are pretty simple so hoping a good strip and clean will sort it

[AshimotoK0]

You need to talk to kent400 on here Paul ! our resident clock repair guru!

[paulbaker1954]

You need to talk to kent400 on here Paul ! our resident clock repair guru!

Ta Ash will pm him

[matthewmosse]

250 superdream clocks are same unit under the covers or as good as, if you can prize the chrome rim off without too much damage you can swap the innards over if a cheap set of superdream clocks pop up, I think the faces need swapping over too but it is a cheap, easy fix.

[Rob62]

Have you tried attaching a drill to the cable to see if the sticky spot is still there....it may be the drive thats faulty not the clock...worth checking first. I have stripped and cleaned clocks before...take your time prising carefully and its not too bad a job....rewarding when completed and a job that can be done at the dining table instead of the cold garage 

[kent400]

The CB500F tacho is a straight cable drive and the Super Dream has an angled one so not sure how that could work. May work on other gauges where the drive is the same, Testing using a power drill was suggested via PM but anyone doing this needs to take a bit of care not to use maximum speed of the drill and damage the tacho in the process.

[Seabeowner]

Rev counter on my K1 is similar in that it's fine to 5k than just jumps around when above this. Built it out of the best bits of two a year ago and its just been taped together this year as I was trying it out. But just about to look inside again.
Is it just a matter of cleaning or is further dismantling necessary or is it likely to be a problem with the damping pot? (it's fairly smooth up and down to 5k.)

[deltarider]

Decades ago I had a speedo that above 140 km/h went wild and the tacho wasn't reliable either. I removed the inner cables, wiped them clean with some petroleum, lubed them with some lithium grease and all was stable. Did this 30 years/80.000kms ago and sofar I did not need to do it again.

[paulbaker1954]

Rev counter on my K1 is similar in that it's fine to 5k than just jumps around when above this. Built it out of the best bits of two a year ago and its just been taped together this year as I was trying it out. But just about to look inside again.
Is it just a matter of cleaning or is further dismantling necessary or is it likely to be a problem with the damping pot? (it's fairly smooth up and down to 5k.)

Hi Phil sounds like we both have exactly the same issue.

When I get some time Thursday I am going to do some testing with drill just to clarify if its rev counter, cable (unlikely as new) or worm drive shaft.

I am in PM on this issue with Kent400 our resident clocks guru so I'll keep posted as to progress.

Not a showstopper issue for me but REALLY annoying

[Dave487]

I have the same problem on my 400. Ok to about 5000rpm then it goes unstable, I haven't really done anything about it yet,  but thought that it coincides with a bit of vibration coming through the handlebars.
I  assumed this is upsetting the instrument and am planning to try new rubber dampers first.

[kent400]

A 'wavering' gauge needle is often caused by the drive cable, draw the inner one out and re-lubricate it as Deltarider suggests. What happens is that the cable revolutions are inconstant particularly the faster the cable turns effectively it's binding. After drawing the inner out if any rust is found on it it needs to be replaced. Correct routeing of the cable is important if a bend in it is too tight the cable will bind.

These magnetic gauges are quite a simple device the usual faults, partially seized at the drive end and this can be checked with a match stick. You should be able to turn this easily and if not add a few drops if light oil. In the case of the speedo it may have partially seized mileage counter gears and the gauge would need to dismantled to resolve that. Rust flakes attracted to the internal magnet and that comes from a base that's corroded on the inside. Ineffective gauge damping, this also be checked with a matchstick by spinning the drive and stopping while observing the needle. The needle should gently drop to zero. The damping effect can vary from gauge to gauge but as long as there's some it should be OK.