Clock decal overhaul

[kent400]

That's dire inside, the base should really be re-zinc plated. I would quite expect some rust flakes have been attracted to the magnet. If you take off the cover secured be the screws both sides of the frame shown in the second image you might be able see what's stuck on the magnet. I have seen bases so badly corroded that they have holes in them

[Lobo]

Lateral - nay lazy - thinking.... any mileage in perhaps forming a plastercine 'cup' abouts the top of the sealed damping pot & filling with oil / leaving to wick in over a day or two? Sounds a whole less fraught than drilling... though I guess the viscosity may work against us.

And thanks Peter, you've got me thinking... I definitely remember my 750 speedo needle 'returning' to 0 in a lovely damped motion... will now have a look at the cable. (though it is brand new, freshly lubed, along with the wheel gearbox). The same-vintage rev counter needle suffers no such bounce.

Just to be sure folks... this 1972 speedo needle should indeed be rock steady.... before I start tearing things down!?

[simonster]

Thankyou kent400. It was rust that had collected on the magnet which was dragging along the casing. Cleaned and now working fine. Will be paint removing the outer casing on the brass brush wheel and then polish it opposed to repainting, it to suit the look of the bike. I'm hoping the steel outer cone can be finished in this fashion without it rusting up too quickly. Does anyone else have any experience refurbing these clocks to a polished finish and how does it weather unlaquered but wax protected? Cheers


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[kent400]

To answer Ash and Lobo's question 30000 weight silicone oil seems to work best for CB750f gauge dampers. For those who don't know the common use for this is diff oil for radio controlled cars. Several listing for it on ebay. Only a few drops is required. Quite often they don't need any attention and if the gauge exhibits some damping they are best left alone.

A wavering needle can often be caused by the cable, effectively it slows down and speeds up as it revolves. Consequently the needle fluctuates. A speedo or tacho can be tested using a drill providing it will run in reverse, if the test shows no fluctuation of the needle chances are it's the cable. Incorrect routing of the cable can cause the inner cable to bind in the outer. Tacho cables seem to suffer more than speedo ones, they are shorter and often route across the top of the engine which seems to shorten their life. So don't attack the gauges before you check the cables. I've had gauges sent with info they don't work and they do! The problem was a broken cable.       

[simonster]

Just wondered if anyone knows where to source the face dial screws and the trip knob screw. I have managed to removed them ok, but the originals are rusty. I've  tried watch repairs, model shops can't get anything anywhere close to the little blighters.


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[Bitsa (Ralph Wright - RIP)]

Could try asking Lecram he is a dial restorer and a member on here
Cheers
Bitsa

[kent400]

The trip knob screw is a problem, tiny screw that won't often come out. I think Ash might be the one who has a selection of tiny screws. I have a selection of dial face screws, I think some 500f gauges used screw with smaller heads although the thread is the same, from memory it's the gauges with metal faces that have the smaller head type. I think they were originally passivized black. You could just touch them up with some matt black paint but if you don't want to do that I'll have a hunt in the spares box and see what I can find

[simonster]

Yes I had to carefully drill the head on the trip screw to release the knob which allowed me to get to the screw to remove with pliers. The thread diameter on that screw is 1.9 mm and 2.2 for the dial facia screws. The heads are different on the speedo and tacho but the threads are exactly the same and I don't mind at all the head type just that they match in pairs. Don't make it a special search, I may just clean and touch up the heads to save the headache. Btw I have just tried a 1.6 mm watch screw for the trip knob and it holds fine. So just need to fix the dial screws. Cheers all.


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[simonster]

M2 stainless works well as a non standard replacement for trip knob and m2.5 for the face plate. Both M sizes are are about 0.2 mm smaller than metric mm and so diameter and thread are a nice tight fit.


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