Odd Speedo behaviour

[Jon T]

Hello folks,
I wonder if you could shed some light on the odd way my speedo is acting? The bike's an 88 R100GS, so small round headlight & large Motometer speedo. Since the winter, on cold days the speedo seems to lose accuracy, the needle wavering around and lagging behind changes in speed, particularly holding on to speed as I slow down. Any ideas what's going on? At 42000 miles and 20-odd years old, could it be that it needs a rebuild? If so, does anyone in the Warwickshire area do them, and for about how much? Any other ideas as to what's going on? It seems odd that on warmer days the symptoms aren't so obvious...
Thanks for any thoughts, Jon

 

[Buz]

I only have a 650 GS so know very little but on here earlier was someone with a GS who had issues with his GS putting on phantom miles, this was down to a naff battery. May be worth checking....
Someone with more knoledge will be along shortly......bit like buses!

 

[Kenny]

I replaced the cable on mine during a bleak winter...I think moisture had gotten into it and the inner cable was rusting/freezing...but changing the cable cured mine

 

[Fanum]

Hello folks,
I wonder if you could shed some light on the odd way my speedo is acting? The bike's an 88 R100GS, so small round headlight & large Motometer speedo. Since the winter, on cold days the speedo seems to lose accuracy, the needle wavering around and lagging behind changes in speed, particularly holding on to speed as I slow down. Any ideas what's going on? At 42000 miles and 20-odd years old, could it be that it needs a rebuild? If so, does anyone in the Warwickshire area do them, and for about how much? Any other ideas as to what's going on? It seems odd that on warmer days the symptoms aren't so obvious...
Thanks for any thoughts, Jon

You've got such a great avatar pic that i've done the work for you.....
CLICKETY

(if that doesn't help, type in 'R100GS speedo' into the search button box and sit back for a read )

 

[BillN]

John T

Speedo problems can be common on Airheads, sticking, jumping around, etc., etc.

Only two possibilities, the Speedo head or the cable.

What I do is to first "swop out the head" - I have a spare Speedo, (it is easier than swopping the cable), and then if no joy, swop out the cable.

Hopefully it will be the cable............you can either replace it it try running some light oil - 3 in 1 down the inside of the cable........take the gearbox end off so it runs through and also check that it is connected and "pushed" down properly

If it is the head.......they are about £170 new or about half that "well used".......you may find one on EBay.........but as you know the Speedo is driven by the gearbox and as the ratios are different between the 80 and the 100, just make sure you get the correct one, W715 for the 100, (the 80 is W1244) - small green numbers just above the reset button for the trip miles.

Good luck


Make sure you buy the one for the R100GS

 

[Voyager]

Mine used to wave about and mis-behave. This went on for a couple of years (1989 R100GS).

I changed the cable - but it wasn't that

Then one day it started reading 90mph at a genuine 50mph, then the needle shot around to the stop and broke off.

It seems they only last for 50,000 miles or so.


I bought a new one and its fine.


I found this Co. who could repair it - but it could take 8 weeks and I couldn't wait that long. Cost estimated to be around £80.00:

www.speedycables.com


I keep meaning to send the old one away for repair. but I've got better uses for £80.00


Bob.

 

[BillN]

Should have added that it also depends on the rear axle ratio, (of course), as well as the gear box

 

[Kenny]

Should have added that it also depends on the rear axle ratio, (of course), as well as the gear box

Final drive ratio is only what is transmitted to the road ( real speed )...gearbox is where the reading for the speedo goes (recorded speed) !!

Someone on here was selling a speedo or two

 

[BillN]

Final drive ratio is only what is transmitted to the road ( real speed )...gearbox is where the reading for the speedo goes (recorded speed) !!

Someone on here was selling a speedo or two

That's me selling the two R80GS Speedos, (plus a load of other Airhead stuff and maybe some Oilhead junk!), ..............but in my view they will not be accurate on a R100GS...........unless you change the rear drive, (I think - but that is a point that we could debate).

and that was why I indicated that the W number on the Speedo relates to the calibration of the Bike with the factory gearbox and rear diff.....if you change either, (but probably only the rear drive is likely to reduce revs at cruising), the Speedo will not be accurate

The real speed is how fast you are going and that is what needs to be indicated on the Speedo!

 

[Shep]

It seems they only last for 50,000 miles or so.

You may be right, mine on my r100 was changed at around 58,000

 

[Spout]

Since the winter, on cold days the speedo seems to lose accuracy, the needle wavering around and lagging behind changes in speed, particularly holding on to speed as I slow down. Any ideas what's going on?

Jon,
you'll probably find the inside is all rusted up (the actual needle mechanism). It'll be worse in cold/damp conditions due to moisture in there (comes up the cable from the gearbox as vapour, or directly through the trip reset button). Is there signs of condensation on the glass?
Getting inside to have a look will be fun BTW

 

[Jon T]

Thanks for the excellent replies chaps. Sounds like it's worth me having a squint at the speedo cable, then if all's well there I'll have to spring for a new speedo - or ignore it! Funny thing is, on a warm day like today it worked fine.

Cheers, Jon

 

[BillN]

also look at the routing of the cable just to make sure there are no snags

"Warm day like today it looked fine and on a cold day you have problems"

really interested to find out why

Good luck

 

[Voyager]

"Warm day like today it looked fine and on a cold day you have problems"

really interested to find out why

Good luck

Probably the damp getting in.

My old speedo used to fog-up in damp weather, probably because the rubber cover on the trip reset button was missing.

Bob.