What is necessary to change an airhead speedo ratio to another?

[XTrovert]

Hi I am not sure if the question is well formulated in English but the issue is as follows:

Have a speedo R80G/S W=773
Needle is crazy, odo went to zero, nothing seems to work.
Can't find direct swap.
But was offered a W=747
What do I need to change and were to make this speedo work accurately

Question #
If I buy a W=773 speedo from another bike can I use the guts of that one to repair mine and if so what chance I hae of success? The issue with the other speedos is the location of the trip meter, unsuitable for the R80G/S pod.

Yes Yes I know I should buy a vapor but I got a Sigma as a spare and well I am stubborn and old bikes are to be kept original and functional so I want to fix this.

Besides I do not like to have to concentrate on small screens prefer a needle for easy reading.

Thanks for clarifying this and or suggesting another alternative, but I want to fix this speedo!

[Wirespokes]

From the numbers you listed, I'm guessing those are metric speedos? And I'm guessing that the one you've been offered is a taller ratio. Perhaps it's the one that came with the R80ST for the optional taller final drive. If you install that one, you'll probably read close to right on or maybe lower than actual speed, but the odometer will show less than actual distance travelled.

The bezel will need to be removed to replace the speedo, so why not take a look at it first? A lot of times the problem is water entering through the reset button and rusting the mechanism. Perhaps the rust can be cleaned up, the mechanism lubed, and it'll work again.

Worth a try!

[boxerkuh]

This is nothing new to us Airheads.... I would open the old set up and see what is going on. A lot of pieces are plastic and after some time give up or jump out of place. It may be a simple fix. You will not know until you open it up. Any Airhead speedo will work, but you will have to calculate the differences based on your stock set up (speedo and rear drive) and what you are replacing it with... You may be able to get a used speedo and and harvest the parts and fix yours...

[Wirespokes]

I hadn't compared the two - the G/S style and the regular airhead style - but think they're way different and not interchangeable. Usually I notice things like that.

It is possible to mount the regular airhead gauges on the G/S (seen it done) so know it can work - and it looked pretty good. Don't know how they'll survive on a G/S though. But you mentioned wanting to keep the bike stock, so that option is out.

[Frank06]

This information was valuable to me and helped me fix my odometer:

http://www.airheads.org/content/view/160/98/

[Paragon]

The 80GS and 80G/S Speedos - mono and para - are the same
R80GS & R80G/S MPH/KPH = W1244
3.36 (RATIO 37.11 SPEEDO 1.244)
The older Speedeos would have been expressed this as 1.244 rather than 1244

W773 = R80G/S and R80ST KPH only

W means 'Wegsteckenzahl' ('travel-distance-index-number'), which equals the number of rotations for 1Km and/or 1mile (a mile would need more W's) travel on the speedo - this is both for recorded mileage and speed

to answer your question - the speedo matches the rear drive ratio

Hope this helps

[Straypuss]

You might find this thread informative..

http://www.advrider.com/forums/showthread.php?t=196637

[XTrovert]

hey thanks to all for the amswers but I am none the wiser.

Yes the speedo is Km/h
But not all the speedos in Km/h are the same.
I have a 773, I can see one which looks the same and is also in Km/h but is a 747

I cannot play with the broken speedo. I am about 10000 miles from the bike!
I cannot send it to a repair shop and wont have the time to do that.

I wonder if it is worth to buy the guts of another speedo or the 747, or it is just a lame idea and a waste of time and money.

Or if I can buy a R80 speedo and use the guts.

Thanks

[Paragon]

Simply put

If you fit the 747 - and if it fits, it will be 3.5% different, (less accurate), than the 773.

i.e. the rear wheel on a standard R80G/S turns 773 times per kilometer and that is why it needs a W773.
The normal R80 rear wheel turns 747 times per kilometer
Don't ask me why they are different

The correct Speedo for a standard R80G/S is W773 or W1244

You should be able to pick one up for under US$100 - used

BM Speedos are not particularly accurate - if you want complete accuracy, use something else

[peterg123]

would very much appreciate your expert advice. My 81 R80 has of course Motometer W1244. These are impossible to get new any more. But I have found for a good price a brand new W1202... claimed to be off a BMW R80 GS ( not G/S) so I preseume a paralever. When I lkook up the part number on a BMW fiche it says in the notes "I=3,20 MPH" . The part is 62121244647

My gut tells me this is a Para R 80 speedo, and will wrok perfectly on my 37/11 ratio stock 81 R 80 G/S. Or am I all screwed up?

Here is the link http://www.realoem.com/bmw/showparts...=62&fg=05&hl=4

I am sure you know them..a very good factory fiche.

Hoping to hear soon as this speedo will not be around long!

[The Raven]

Originally Posted by peterg123

would very much appreciate your expert advice. My 81 R80 has of course Motometer W1244. These are impossible to get new any more. But I have found for a good price a brand new W1202... claimed to be off a BMW R80 GS ( not G/S) so I preseume a paralever. When I lkook up the part number on a BMW fiche it says in the notes "I=3,20 MPH" . The part is 62121244647

My gut tells me this is a Para R 80 speedo, and will wrok perfectly on my 37/11 ratio stock 81 R 80 G/S. Or am I all screwed up?

Here is the link http://www.realoem.com/bmw/showparts...=62&fg=05&hl=4

I am sure you know them..a very good factory fiche.

Hoping to hear soon as this speedo will not be around long!

If you are talking about the speedo from the guy in France on Ebay I bought one for my G/S.

Yes it worked, but at an indicated 70, I was doing about 62. Kind of annoying, but I just did the conversion and liked the odometer for fuel fill ups.

[stickerbush]

Originally Posted by The Raven

If you are talking about the speedo from the guy in France on Ebay I bought one for my G/S.

Yes it worked, but at an indicated 70, I was doing about 62. Kind of annoying, but I just did the conversion and liked the odometer for fuel fill ups.

Most of that difference is due to the 'optimism' of the original speedo. The difference between a W1202 and W1244 is only about 3.5% or a bit over 2mph at 62.