Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: simonster on November 09, 2014, 12:10:22 AM
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I'm in the process of restoring the clocks on my 72 500 k1. I've opened the speedo by uncrimping the band and have ordered new decals. But I've got to the stage of removing the needle and have read two ways of safe removal, one being to prize the needle vertically off the shaft or the other to rotate the pin anti-clockwise beyond the 0 position. Has anyone tried either technique with any success?
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Until Kent400 (Peter) steps in... the forum guru on clock renovations...
I've done 4 clocks, with complete success by using the 2 teaspoons under the needle boss method. Simply put them opposite each other, as close to the spindle as you can get, and gently lever the needle up symmetrically. It'll come off with a ping... ie don't do this near open drains / a nice roaring fire what-have-you.
Don't at all like the sound of rotating the pin beyond the 0 position, sounds fraught for bending it!
Simon.
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I have used a fork with good success in the past,
pete
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Two spoons work a treat but as lobo states whatch where it goes I spent 15mins grovelling under my bench trying to find one ;D
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Two spoons work a treat but as lobo states whatch where it goes I spent 15mins grovelling under my bench trying to find one ;D
Did one years ago Paul in the kitchen. Thought it would be the safest place to find the needle again. Wrong, it hit the ceiling and as far as i know went down behind one of the wall mounted cupboards. 16 years on i still have not found it.
when using a teaspoon or any other method, put a towel over the clock.
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Yes two teaspoons is the best method, position them so the underside of the spoons are resting on the dial face screws and provide the same pressure on both sides to avoid bending the needle pin.
Hope you put a large hose clip or clamp around the band before you lifted the edge of the base otherwise the band can be distorted and a blighter in the to re-crimp.
Good luck with them
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Cheers for all the advice. The two spoon method worked a treat. No I didn't use a clamp around the band, kent400. I just took it real steady with ascending sized flat drivers and was pretty pleased with the result. I can see how the clamp would make it less likely to damage the band and clock cone and will use that method on the rev counter and post the end results.
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Also, I used cling film over the face when I popped the needle. Same idea I know , but being the novice, made it easier to see what I was doing.
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Oh, cling film over the needle sounds quite a good suggestion. I just use a duster but I suspect needles have ended up in some interesting places, cat litter tray anyone?
Using a hose clip around the band before removal prevents the band bending outwards as it's removed, there's only about 3mm of the band folded over the base. If the band is bent outwards you end up with even less to fold back over the base.
On the larger CB750f type there's even less of the band folded over the base so even more essential to clamp the band before removal. Also a good method to use on those gauges were a bezel holds the glass. Bit more of a problem if the gauge isn't round, square ones are tricky but a hose clip can still be tightened and will more or less take the shape of the bezel.
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Hi Peter..
Whilst you're here (!) can you perhaps pen a few words on how to fill / top up the damper pots in these instruments? My 750 speedo fluctuates +/- 5mph .... assume not normal, even for 1972.
Cheers,
Simon.
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Hi Peter..
Whilst you're here (!) can you perhaps pen a few words on how to fill / top up the damper pots in these instruments? My 750 speedo fluctuates +/- 5mph .... assume not normal, even for 1972.
Cheers,
Simon.
Yes I would like to hear from Peter too on this but I have asked before here on the USA site:
http://forums.sohc4.net/index.php?topic=78890.0
Lecram has a video of before and after but don't think specifics of how to do it.
I have a litre of silicone oil but need to get it's viscosity measured.
Cheers ...Ash
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Having just opened the tacho and found it in worse internal condition to the speedo. With some metal decay around the inner base. The working mechanism has discolouration on the load spring ( don't know the correct term ) and turning the needle manually does cause it to unload back to its original position most of the time... However it occasionally sticks and I can feel some resistance on the needle shaft. Is this serviceable? Can I lubricate? I know there is some mention of using silicone oil in this thread but no definitive answer. Will spray quick dry solvent help in the first instance to clean up before lube. Cheers
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The chances are that some rust flakes for the inside of the base have been attracted to the internal magnet that's connected to the drive and are jamming the aluminum magnet cover. If that's the case you might be able to remove two tiny screws on each side of the frame and lift off a small aluminum shield to gain some access to the magnet. Beyond that you have to grind off the barbs that secure the front of the frame to the remainder. It then possible to remove the magnet cover but this is a tricky business, especially re-fitting.
As for the dampers, differant types on the smaller gauges the front of the gauge has to come off and the silicone grease replaced. Again a tricky business. Several differant types of dampers one the larger gauges, one you can remove the end cap to refill, great care required. The other type a hole is drilled in the damper to refill. A wavering needle isn't always due to lack of damper fluid, the drive cable can be the cause. A easy test for damping is spin the drive end, if the needle drops instantly to zero there no damping effect. The damping effect does vary a bit in so far how quickly the needle drops to zero but it should not drop instantly when the drive ceases. Hope that helps
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On forgot to mention if the tacho mechanism is beyond repair I may well have one in the spares box.
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Thanks for that advice. There is definite damping on the needle because when it does return there is that nice millisecond delay before smoothly unloads to zero. This is how it looks if you could advise on the type of mechanism I have. Cheers
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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
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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!?
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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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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.
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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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Could try asking Lecram he is a dial restorer and a member on here
Cheers
Bitsa
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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
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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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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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