78 R100RS Speedometer Question

[airraceaddict]

Can anyone explain how the speedometer actually works? The odometer and trip meter are obviously direct drive. My speedo was making a terrible noise and jumping all over the place. Odometer and trip meter seem to be spot on. With speedo cable disconnected, the needle is still jumping around all over the place, even sitting still. Help? I know I can send it to PA Speedo and get it fixed for around 275. It seems there should be something I can do. I am pretty good with instruments. Aircraft mechanic and all........... Thanks

 

[20774]

Have a look in this file:

http://forums.bmwmoa.org/showthread.php?t=47142

There is a section on speedometer repair. One article takes you through disassembly in order to repair the odometer/tripmeter numbers which might not be connecting and turning, but it helps see how things come out. Another article talks about the process to adjust the accuracy of the speedo.

Basically, the needle is not directly attached. At the extreme end of the speedo cable sits a sort of cup. The mating end of the needle sits inside the cup, but not touching it. The cup spins and uses magnetic force to turn the needle. There is a spring in there which helps returns the needle to zero and provides damping. If your needle is jump without the cable connected with engine running, I'd say the spring is kaput.

 

[doktortim]

Can anyone explain how the speedometer actually works? The odometer and trip meter are obviously direct drive. My speedo was making a terrible noise and jumping all over the place. Odometer and trip meter seem to be spot on. With speedo cable disconnected, the needle is still jumping around all over the place, even sitting still. Help? I know I can send it to PA Speedo and get it fixed for around 275. It seems there should be something I can do. I am pretty good with instruments. Aircraft mechanic and all........... Thanks

I concur. The only way the needle could jump around without any input from the cable is if the spring is broken. Long before I sent the speedo head to PA or anyone else I would discuss it with Terry Vrla (terryvrla@hotmail.com) He has been servicing Airhead instruments for many years. He is very upfront and an honest Joe who loves fixing Airheads. He's got hundreds of little drawers with little screws and springs and gears and shafts and knows where they all go and how they all work.

 

[airraceaddict]

Thanks, I will contact Terry as you suggested Herr Doktor Thanks to you both for the input. I know I can fix it if I have the correct parts and information. I will let everyone know what I find out.

 

[georgej]

Terry is a good man and does good work. He repaired/rebuilt the speedo/odometer on my '78 RS. A very either way nice guy to deal with. I've had Overseas Speedometer do work on other airhead speedos and would use them again,but Terry was a little less expensive and he took a broken spare speedometer I had as part of payment.

 

[20774]

Perchance to Terry have a website? I didn't find anything right away...

 

[doktortim]

Perchance to Terry have a website? I didn't find anything right away...

If you go to ADVRider.com he is Wirespokes on there. There is a link in all his posts for instrument fixin".

http://www.advrider.com/forums/index.php

He is in the Old's Cool section just about every day.

http://www.advrider.com/forums/forumdisplay.php?f=35

Whoops's, no link in his posts currently. Just shoot him a pmail from there or use the address given above. Here is a recent post.....Just scroll down and find Wirespokes.

http://www.advrider.com/forums/showthread.php?t=680195

Wirespokes
Beemerholics Anonymous
Joined: Jul 2002
Location: Oregon's Scenic Jackson's Bottom
Oddometer: 5,881

I am in there as DoktorT. Andrew Lardigare is there as well from time to time. Like any public forum you must separate the wheat from the chaff, but there is as much good experience and knowledge there as here. A greater percentage of posers so just take care and confirm info outside your own area of experience with someone you trust before you reach for your wallet.

 

[doktortim]

Thanks, I will contact Terry as you suggested Herr Doktor Thanks to you both for the input. I know I can fix it if I have the correct parts and information. I will let everyone know what I find out.

Say Bill, I see you are in Cheney and have a Gold RS?? Were you up in Deer Park a coupla weeks ago at the Airhead gather at Bob Dash's place?? Or at Republic the following week? Hope that PPG Gold doesn't turn Lizard Vomit Green in a few years like the stock paint did.

I have a 79RS and am in Spokane. Shoot me an email and let's ride soon. I can show you just how to get inside that there speedo in no time if you want to come over. Get over here. Or I could come out there.

 

[airraceaddict]

Hey Tim,
Thanks for the contact. I didn't notice you were in Spokane. Yeah, I was in Republic. Didn't get in until Saturday afternoon. It was a good time. I love that ride up through Keller then over Sherman Pass on the way home. I got in touch with Terry and he gave me a suggestion for the speedo. We can get together at one of the meetings this week hopefully and we can chat about the bikes.
Bill

 

[airraceaddict]

Have a look in this file:

http://forums.bmwmoa.org/showthread.php?t=47142

There is a section on speedometer repair. One article takes you through disassembly in order to repair the odometer/tripmeter numbers which might not be connecting and turning, but it helps see how things come out. Another article talks about the process to adjust the accuracy of the speedo.

Basically, the needle is not directly attached. At the extreme end of the speedo cable sits a sort of cup. The mating end of the needle sits inside the cup, but not touching it. The cup spins and uses magnetic force to turn the needle. There is a spring in there which helps returns the needle to zero and provides damping. If your needle is jump without the cable connected with engine running, I'd say the spring is kaput.

Thanks Kurt. I looked at the link and there it was, a drawing and everything that really helps me to understand how the thing works. And with Terry's email back to me and the other help here, I think I know how to proceed. Thanks again.
Bill