Fluctuating Speedo

[TZOLK]

Anybody savy to a Speedo that hunts around 5 mph while at speed. Like while going a steady 60mph it bounces between 60 and 65ish. Is this a sign of a worn out cable or speedo or ?

[bmwmick]

Todd,
It 'could' be a worn cable or just in need of some lube. My '84R100RS had this problem last year. It would be fine until I maintained 70 or so for more than 30 minutes. At that point it would start fluctuating about 10MPH at anything above about 40MPH. I lubed the cable but that didn't help. Next I removed the instrument pod and disassembled the speedo gears. All the lube (white lithium) had dried out. I re-lubed the main gear in the speedo itself and it has been rock steady ever since. Go here: http://www.airheads.org/ and look through the speedometer fix articles. This picture: http://www.airheads.org/contrib/images/speedo5.JPG shows the gear drive housing that you take apart to re-lube.

[The_Veg]

I'll second Mick's answer but I'd fully eliminate the cable being at fault (from either wear or lack of lubrication) before tearing into the instrument.

[bigb]

I have a 82' R100RT and was on a long trip and my speedo started doing the same thing, I thought I could deal with it when I got home. Well it didn't make it and the needle started spinning around real fast and broke the needle off. I spent the the rest of the trip without a speedo. I had to send it off to Palo Alto to have it fixed, and it wasn't cheap. I would oil it first and if that doesn't work get a new cable. (like Mick said) 15 min job tops, real easy. :drink

[James.A]

I've had more broke speedo's than you can shake a stick at. Take it apart and lube it before it goes puhhhh.

[TZOLK]

I took it off the other day and it looks like you have to pry the big black metal ring off in order to get the guts out. Know how to do it without marring it all up?

[James.A]

Todd, I can't help you with that. /5's are a bitch to get open. They have a crimped bezel around the glass. /6 and /7 are easy. Their Honda-looking instrument set un-screws from the backside. I've never fiddled with a newer airhead. A crimped bezel must be patiently un-crimped with a hooked tool.

BTW, you should first lube the cable until you are satisfied that the cable is not the cause of the problem.

[TZOLK]

I chiseled off the nice black metal ring cover :cry and got to the ingredients. The speedo isnt operated off any worm gear or such. The worm gears on the side are for the ODO. The speedo needle seems to turn by magnetic grip? Hell, Im not sure how it works. The part that hooks to the cable is this wheel and that wheel fits into a Hub like thing that is directly attached to the needle. But the wheel and hub dont seem to touch. If they did, the needle would rotate and snap off with just a little movement. The wheel sorta floats inside the hub. So there is really nothing to grease other than the ODO gears, which I did anyways. May need a new one eventually, and or a cable. I lubed the cable but it still does the wiggle.

[bmwmick]

Todd,
Did you click on the link I provided above? You disassemble the drive gears
by removing that little RED screw. Once you pull the BIG threaded piece out you will see the bushings inside that dry out.
You are correct, the speedo cable drives the shaft with the worm gear which turns the hub with the magnet. There is a gap to the needle cup and the needle cup has a pice of ferrous metal on it. The magnet drive is what counteracts the clock spring that is holding the speedo needle at 0.
Sounds like you didn't get it lubed where it needs to be lubed.

[TZOLK]

Oh yeah, while it was apart, all bits got lubed. ODO gears, the main shaft thingy that runs off of the cable. I lubed that with lithium grease. Will have a test run later today. see what happens.

[rocketman]

I have yet to ride a /5 that didn't have at least a bit of a wobble in the speedo and becuase of the magnetic drive they are none to reliable as far as actual speed vs indicated speed, just part of the joy of riding older machines. :D

"but officer, its 30+ years old, how old is YOUR bike!??"

RM