Author Topic: Speedo damping?  (Read 2337 times)

Offline Arch stanton

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Speedo damping?
« on: July 28, 2018, 09:37:20 PM »
Hello.
I have a 750f1 speedo apart for refurb, but it has no damping.
What substance should i use & where do i put it?
Obviously i dont want a bouncy needle on a rebuilt speedo.
I already have clock needles like windscreen wipers on my T500. Most annoying.
So your help would be appreciated.
Sean.

Offline Skoti

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Re: Speedo damping?
« Reply #1 on: August 01, 2018, 05:55:04 PM »
Motorcycling is Life, anything B4 or after is just waiting...


1976 Honda CB750F1

Offline Arch stanton

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Re: Speedo damping?
« Reply #2 on: August 01, 2018, 11:14:35 PM »
Thank you for your willingness to respond.
I have taken your advice.
Sean.

Offline AshimotoK0

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Re: Speedo damping?
« Reply #3 on: August 02, 2018, 12:03:38 PM »
Never done a F1 only K0&K1 but you need 30,000cst silicone oil like this in the link below. Some people recommend higher viscosity but this worked fine for me. There will be a little pot underneath the top bridge below the needle, which will need refilling. On the 750K0/K1, I drilled this with a 2mm sharp drill bit and filled through the hole, from side top and then sealed it with aluminium filled epoxy. This meant that I didn't have to remove the top bridge, which is staked over and a bit tricky to remove. I used a small syringe fitted with a tiny bootlace ferrure that electricians use, which created a short injection needle.

https://www.ebay.co.uk/itm/Core-RC-100-Pure-Silicone-Oil-For-Diff-shocks-All-Grades-In-Stock-100-300-000/141159428673?ssPageName=STRK%3AMEBIDX%3AIT&var=440235905561&_trksid=p2057872.m2749.l2649

Select 30,000 cst
« Last Edit: August 02, 2018, 12:08:11 PM by AshimotoK0 »
“Alright friends, you have seen the heavy groups, now you will see morning maniac music. Believe me, yeah. It’s a new dawn.” Grace Slick, Woodstock '69 .. In the year of the Sandcast.

Offline Arch stanton

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Re: Speedo damping?
« Reply #4 on: August 02, 2018, 04:00:24 PM »
Hello Ash.
I have looked at a few old threads on this subject.
There appears to be quite a difference between the K1 & F1
Speedo's in the damping pot dept.
The F1 has Very small bullet shaped pot that looks more like some sort of weight than anything else.
I cant think how the damping works.
There is no sign of a seal or joint.
I would post a pic but im a bit of a Dunce in the IT dept.
Sean.

Offline AshimotoK0

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Re: Speedo damping?
« Reply #5 on: August 02, 2018, 04:30:38 PM »
I think I have an F1 opened up speedo/tacho somewhere ... I will take a look.

If not kent400 on here (Peter Horton) will probably know.
“Alright friends, you have seen the heavy groups, now you will see morning maniac music. Believe me, yeah. It’s a new dawn.” Grace Slick, Woodstock '69 .. In the year of the Sandcast.

Offline kent400

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Re: Speedo damping?
« Reply #6 on: August 02, 2018, 05:16:16 PM »
There are a couple of different damper designs used on the speedometer but they can be refilled is exactly the same way. The tachometer may have a different design that has a aluminium cap at the needle end but again can be refilled as Ash described. Where the speedo is concerned the mileage counter needs to be removed by carefully bending back the tabs that securing it to the mechanism frame. Whatever is used to seal the hole in the damper needs to be minimal otherwise it will touch the mileage counter as there is only a couple of millimetres clearance between them. No problem with the tacho of course. None of these have anything that could be described as a seal and leakage usually only take place if the gauges are stored face down.

Offline AshimotoK0

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Re: Speedo damping?
« Reply #7 on: August 03, 2018, 08:12:49 AM »
There are a couple of different damper designs used on the speedometer but they can be refilled is exactly the same way. The tachometer may have a different design that has a aluminium cap at the needle end but again can be refilled as Ash described. Where the speedo is concerned the mileage counter needs to be removed by carefully bending back the tabs that securing it to the mechanism frame. Whatever is used to seal the hole in the damper needs to be minimal otherwise it will touch the mileage counter as there is only a couple of millimetres clearance between them. No problem with the tacho of course. None of these have anything that could be described as a seal and leakage usually only take place if the gauges are stored face down.

Makes you wonder how Honda ship(ped)  those parts as spares  in the post to people without preventing them being upside down at some point  Peter.
“Alright friends, you have seen the heavy groups, now you will see morning maniac music. Believe me, yeah. It’s a new dawn.” Grace Slick, Woodstock '69 .. In the year of the Sandcast.

Offline kent400

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Re: Speedo damping?
« Reply #8 on: August 03, 2018, 05:47:21 PM »
I think it's only a problem if the gauge is left face down for an extended period. If you have ever seen an original box a gauge is supplied in it's marked with the instruction to store face upwards. What I don't quite understand is why some gauges of the same type loose their damping effect and others of the same age don't. Seiki gauges seem to worse as far as loss of damping is concerned. On the early Seiki ones it's only a question of removing the tiny nut under the needle, withdrawing the centre of the damper to re-fill.
Not so easy on ND ones of course.

Offline Arch stanton

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Re: Speedo damping?
« Reply #9 on: September 09, 2018, 06:27:43 AM »
Hello again.
Can anyone explain to me.
How does the damper work?
It appears to me that there is a metal tank of oil with a continuous shaft running through it.
How can that work?
If the shaft rotated within the tank of oil, while the oil tank remaind stationary. Then i could understand it. Just as i could. If the tank was a solid mass & simply acted as a counter weight. But in that case. What is the purpose of the oil?
Sorry if I'm being a bit dense. But i simply dont get it!
You explanations are eagerly awaited.
Sean.

Offline AshimotoK0

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Re: Speedo damping?
« Reply #10 on: September 09, 2018, 07:51:23 AM »
There is a tube attached to the top, fixed bridge of the gauge. The upturned cup with viscous oil in it is attached to the shaft of the gauge and rotates. Therefore,as the cup rotates, there is drag between itself and the fixed tube,caused by the oil, which gives damping to the needle. Just really a classic 'spring & dashpot' damper arrangement but of the rotary variety.
“Alright friends, you have seen the heavy groups, now you will see morning maniac music. Believe me, yeah. It’s a new dawn.” Grace Slick, Woodstock '69 .. In the year of the Sandcast.

Offline Arch stanton

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Re: Speedo damping?
« Reply #11 on: September 09, 2018, 08:46:10 AM »
Hello Ash.
Thanks for your prompt response.
But there is no tube or upturned cup.
There is only what appears to be a solid cylindrical slug of steel which the needle shaft runs through. They are fixed together.
This is a ND F1 speedo.

Offline AshimotoK0

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Re: Speedo damping?
« Reply #12 on: September 09, 2018, 09:51:37 AM »
Hello Ash.
Thanks for your prompt response.
But there is no tube or upturned cup.
There is only what appears to be a solid cylindrical slug of steel which the needle shaft runs through. They are fixed together.
This is a ND F1 speedo.

Kent400 will know ...If not I do have an F1 gauge somewhere I can take look at but I bet the principle will be the same as the earlier gauges.
“Alright friends, you have seen the heavy groups, now you will see morning maniac music. Believe me, yeah. It’s a new dawn.” Grace Slick, Woodstock '69 .. In the year of the Sandcast.

Offline kent400

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Re: Speedo damping?
« Reply #13 on: September 09, 2018, 10:56:31 AM »
Here is an F1 speedo showing the damper, I'm assuming the face i the same as you have with the km/h marking on the dial face. You can see the aluminium damper, you can see where I drilled it and subsequently re-filled it. The dark spot on it where the hole is sealed.

Offline Arch stanton

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Re: Speedo damping?
« Reply #14 on: September 09, 2018, 12:08:04 PM »
Hello Kent.
Yes that is the same as my Speedo.
But what difference can the oil make if its in a cylinder
That moves with the needle shaft?
If the shaft moved through a fixed cylinder of oil, them there may be some resistance thus damping.
But surely. If the shaft +oil+cylinder all rotate in unison.
Then the result would be the same. Oil or not.
Wouldnt it?
Like i said. Sorry if i appear dense. But i dont get it.

 

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