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Refilling Dashpots on CB750K0 Gauges
AshimotoK0:
Well I ordered the silicone oil and the Revell orange paint for the needle tip. I found that the tacho drive was almost completely seized up. I removed the top bridge with the hairspring intact and no worries there. However, I couldn't remove the gearbox housing from the steel base. There is another cast alloy plate alloy with three mounting screws that also carries a brass bush. This plate has a boss that locates into the gearbox and I found this boss was seized to the gearbox housing. You can't remove the plastic worm gear and its shaft without pulling the gearbox housing off at least partially. This plastic gear prevents you from applying any real heat to free it off plus I would image any heat might partially demagnetize the rotary magnet. Long and short is I tried every method to remove it and then CRACK, the plate with the boss on it cracked and I still can't pull the gearbox off the base plate. The only way I reckon I can get it apart now would be to somehow press the brass gear off the shaft but I'm not sure if the gear is a press fit or pinned onto the shaft. In desperation I bought a damaged K1 tacho mechanism from DK and I am hoping that I can graft this into my K0 unit, if the gearbox on it is serviceable. I guess Lecram may be the guy to ask but his website says he's on holiday. Any advice Peter?
kent400:
Hi Ash, I've never had much of a problem getting the angle drive off once I've removed the three screws and just twisted them. The problem is that the aluminium corrodes on the small portion of the angle drive that's inside the base and expands. It's been a while since I had a gauge of that type though my hands so I can't recall the exact details other than the fact that once the angle drive you are left with just the plastic gear protruding from the base.
I suppose all you can do is to soak it in some rust remover for a couple of days, something that's mildly acidic. Heating won't do much good as the it will probably cause it to expand.
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