SOHC.co.uk Forums > CB750
Refilling Dashpots on CB750K0 Gauges
AshimotoK0:
Anyone successfully refilled the dashpots on CB750K0 gauges? If so, couple of questions:-
1) What viscosity silicone oil did you use 30,000cSt or 50,000cSt ? ( I think Marcel at CB750faces uses 50,000 and I guess he's the man on these but other people suggested it's too viscous)
2) Did you unglue the lid on the dashpot and re-glue after topping up or drill a hole in the side, inject oil and re-seal?
kent400:
I've always used 30000 cSt on ND gauges effectively and drilled a small hole is the damper to replenish You need to exercise care of course, once a few drops of silicone has been added move the needle around and add some more until the damping effect returns.
The damping effect does tend to vary from gauge to gauge slightly but what you need to see is a needle that does not drop immediately to the stop when the drive is spun.
AshimotoK0:
--- Quote from: kent400 on July 11, 2018, 01:10:53 PM ---I've always used 30000 cSt on ND gauges effectively and drilled a small hole is the damper to replenish You need to exercise care of course, once a few drops of silicone has been added move the needle around and add some more until the damping effect returns.
The damping effect does tend to vary from gauge to gauge slightly but what you need to see is a needle that does not drop immediately to the stop when the drive is spun.
--- End quote ---
Thanks Peter... the K0 speedo I have appears not to have a cap on the dashpot ..its just a brass tube within another brass tube .. I will try to photo as it may help others. The tacho dashpot is an alloy cup with an alloy cover and the cover is glued to the cup. So it's a case of make sure the gauge is always stored upwards.
kent400:
I think there were two different designs of damper type on ND gauges and I would have thought that two gauges from the same bike would have been the same design. The two types I have here is one with the aluminium cap that has a sealant around it, the other type that has no cap and is a smaller diameter. The second type I found in the spares box, I can see I have re-filled the damper and that's a speedo mechanism. Looks like I used most of it for spares and I rather think I may re-sealed the hole made in the damper as an experiment to ensure the seal was effective. Clearly it was.
AshimotoK0:
The speedo has the open type damper but is definitely original to the bike, as it's consistent with old MOT's I have. The tacho may well have been changed by a P.O. but it has the sandcast type gearbox drive and it has the alloy style damper with the cover (cover secured to the body with dabs of dark brown adhesive or whatever). The damping doesn't seem too bad on the tacho, so I may leave well alone on that one.
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