CB750K Speedo Recon... help pls

[Lobo]

Hi,
Guess one for Peter / Kent400, but happy for anyone to chime in.

Am reconditioning my 750K2 Insts, as a recent eBay kph speedo came with a mismatching face to the RPM gauge.

Anyhoos, whilst I’ve now done a few gauges, I’ve never yet tackled the damping; in this case there is none (!) and so I guess the time has come.

The inst is fully dismantled tho’ fallen short (for now?) of grinding away the ‘once only’ tabs which (1) capture the top plate and (2) the total kms tumbler.

Cheers in advance,
Simon

[kent400]

Hi Simon,

The easiest way is to drill a very small hole in the damper ( I use a hand drill ) of course the damper pot will try to revolve so lock it with a small piece of wire to the speed cup rest tab. Add some 100000 silicone oil, it's quite thick so push it into the hole and turn the speed cup to spread the oil around inside.

Takes a while before you will see the damping restored and try not to get silicone oil on the hairspring. Seal the hole with some mastic.

[Lobo]

Hi Peter,
Long time no hear - hope all’s well....

Thanks for the speedy reply.

Just to confirm the circled is the damper pot, and if so is it ok to drill anywhere, or top / bottom / middle preferred? (I presume it includes some internal return spring?)
What size drill do you recommend for this ... is a 01mm ok?

Many thanks,
Simon

[kent400]

Yes that's the damper, it's aluminium and the shaft inside it is brass. A 2mm drill seems the best size to use and the best place to drill the hole is in the middle. This does need great care as you don't want to drill into the brass shaft. You also need to remove the mileage counter if the drill slips you know where if will go!

The mileage counter is very close to damper so when the hole in the damper is sealed if has to be close to flush otherwise it will touch the counter.

[Lobo]

Cheers Peter. Only able to source Silicon 80000 locally.... which I assume is near enough.
Not sure how I’ll squeeze the 750W Bosch Chuck into to the guts of the speedo 😂

Many thanks.
Simon