r80gs getting at the clocks

[luanaigh]

Hello there,
Does anyone have any advise before i open up the clocks on my r80gs. my speedometer dosn't work (its not the speedo cable because the mileage guage works fine). I remember trying to open it up before but failed miserably ( i was afraid i was going to break something )...has anyone tried to do this before???Does anyone have any helpful tips?Thanks in advance.
Barra O Luanaigh
:confused1:

[Frank Warner]

The balck piece at the top need s to be (carefully .. very carefully) expanded ... choose the bit at the back so you don't see it when you reinstall it. Most ordinary mortals will damage it . And geting a new one is difficult. You are probably best off finding a speedo repairer. Once you have it opened .. you may =find a broken hair spring, bearing gone .. you got the watch making skills to fix it? I did 3 months as a watch maker .. it was not easy and my eyes anit what they used to be.

Fitting a bicycle speedometer is easy , and they are cheaper than getting your original speedo repaired!

[Vaufi]

Hey Frank,

sounds like you're stuck in Oz instead of doing the trip you ha planned via western Africa to Europe. I was expecting to catch up with you at the HU meeting in the UK in June. You won't be there, will you?

Hans

[luanaigh]

Thanks Frank,
Sounds messy alright.I'm not much of a watch builder but as the bike is off the road for a while i might give it a bash,,,,
its been annoying me for a while,,,,thanks for the tips and the time,
Barra O Luanaigh

[gsworkshop]

Whatever you are thinking, don't' do it.
You will have no success trying to fix it yourself. Even if you get it to work you will find the calibrating to be out completely. this needs to be done on a special instrument.
The reason it is not working is most likely because the gears is ceased and one or more gears might have to be replaced.
The needle is very delicate and will brake by just looking at it to hard and will definitely be out of calibration just touching it.
I would recommend disconnecting the speedo cable to prevent further damage until you can get it fixed by a professional and buy yourself a cheap bicycle speedo because they can do exactly the same job.
A new speedo for these older bikes is about double the price of one for a new GS, so don't fiddle with it even if you think you can fix it.

[Frank Warner]

Originally Posted by gsworkshop

The reason it is not working is most likely because the gears is ceased and one or more gears might have to be replaced.

Errrr no.
The gears are for the odometer.. that is functioning.

The speedo is direct drive to the drag cup. The bottom bearing (and mount for the cable drive) is plastic (on teh G/S and onwards) and can ware out. Easiest to replace that with a brass piece from an older model bm .. they saved weight (and cost) by going with the plastic bit. And the hair springs can go .. and the needle bearing .. all fiddley stuff. None of the parts are avalible from bmw... a wercked old bm speedo may be a source of parts .. if you can find one.

Calibration can be achieved using an electric drill .. but you'll need to know the speed of the drill (and that will be 'locked' to teh mains frequency - provided it is not a varible speed model) the tyre diameter and the geat ratio on the hub... or in the gear box and final drive for a bm.. - the easiest these days is to use a gps and compare. Adjusting teh reading .. well it is not simple. Depenmds on the adjustment required - if a constant offset - moveing the needle on its splined spindal is easiest. Non constant .. well you have the hair springs..

-----
I hope to be in Africa in a week or two... been saying that for a while. I'll definatly be at the Isle of Man TT, and the uk hu meeting following it..

[gsworkshop]

You are right, if the trip meter works the gears should be fine. The point I am trying to make is that it is not worthwhile to open the speedo if you don't understand the mechanics behind it or if you do not have a way of calibrating the speedo. There is a code on the face of the speedo to relate to the final drive ratio of the particular bike model but you still need an instrument with variable speed where you know the RPM. So the idea is to run the speedo at the rpm that will give you 100km/h or 55m/h with the needle removed and once it is spinning at the right rpm you just push the needle back on.
Removing the cover is also tricky and if you destroy it there is no way of buying a new one.
Spare parts is available but not from BMW as they sell it as a sealed unit with the idea that you should replace it with a new one if damaged.
Your best bet is to take it to a instrument repair facility and in the case of a BMW GS you should find someone that can work on VDO instruments.
Not an easy task as most new electronic instruments can't be worked on and there is a smaller demand for this sort of repairs a bit like a dying trade.
I have a old Belgium guy that is retired but have done this for years working for some of the large instrument suppliers. He kept a small workshop going in the back of his house where he is doing private work for restorers.
If you are prepared to send your instrument to Cape Town South Africa I can drop it at his place and after ship it back. Cost will be around $ 90 US. without shipping.

[yngveer]

Hmm.. many good arguments here.. but if its already broken why not give it a try.. Yes, you can probably ruin it even more, but you can also learn somthing new, and maybe get it to work. If it work, but out of calibration it should be possible to get it recalib. later on...
This is just my opinion.......
Good luck

[Frank Warner]

Originally Posted by gsworkshop

BMW GS you should find someone that can work on VDO instruments.

This is an R80GS .. or is that a G/S .. what ever .. these are MOTOMETERs .. mechanical not electrical.

On the calibration .. you do not need to have a varible speed thing .. just as long as you know the speed and can figure out what the speedo should indicate .. nice to have it at 60, 100 and 150 so you can do linearity .. but if 56.8234234 km/h is what you have then calibrate it there. Personally I find the calibration fairly good after the repair ... but then I've been repairing and calibration things for decades ...

[gsworkshop]

You are right, it does not have to be the exact speed. I think the reasoning behind calibrating at 100km/h is that you calibrate closer to the average speed traveled mostly as the instrument will then be most accurate at that speed. So if you want it to be very precise and you like traveling at 30km/h then rather do it at thirty.
The most important part is to know what the revs is of the calibrating instrument and to interpret that to the code on the speedo so you know what speed it is supposed to be set at.
Maybe Frank can explain how to determine this calculation once you know the exact RPM of the calibrating instrument whether very specialized or a normal drill.
And again you are correct, the instrument on the R80G/S is from motometer, the optional watch and rev counter comes from VDO.

[luanaigh]

Thanks everyone for the great help. thanks also gsworshop for the offer of help from your friend.
I had a feeling that the unit was supposed to be enclosed.Any way looks like i will have to do some looking for spare clocks (for parts).....watch this space as i might be begging for help,,,,, (especially the calibration) i have a very handy friend at this sort of thing and i agree that i will learn something (or is that break????).
appreciate the excellent advise
Go raibh maith agat (thanks in gaelic),
Barra O Luanaigh