I'm Always SPEEDING...........

[captmako]

My '86 R80 speedo runs way too fast - probably 1.5x my actual speed. I did search here and found no info on the subject.
However, I see on the Net the typical airhead speedo has troubles with accuracy. My machine has 40,000 miles on the clock.
I found a nice Iphone app that calculates speed, etc.. Problem is no room on handlebars to mount an Iphone bracket.
Can the speedo be successfully repaired or.......?

[Kurt in S.A.]

Assuming that the final drive ratio and speedo ratio are a matched set, BMW is known to have purposefully set the registered speed to never be less than actual speed and up to a maximum of 10% of actual speed plus about 2 mph. There's a service bulletin to this effect. Tire sizes also have an effect.

Yes, it can be successfully repaired (or at least minimize the difference)...typically people send them off to Palo Alto, North Hollywood, Overseas, etc. You can try it yourself...pretty delicate stuff in there. See this page:

http://home.jtan.com/~joe/speedo.htm

Kurt in S.A.

[Duane Ausherman]

It will probably come back from a rebuild with the same error. If you find a small shop and actually talk with the person, maybe you can get it recalibrated.

[captmako]

Thanks Kurt and Duane. Not sure what I'll do at this juncture. I'll ponder on this one.
I appreciate your input.

[Major Softie]

50% high is unusual. I haven't heard of any mismatch turning out THAT far off. OTOH, I haven't heard of one reading that far off from an internal failure without it exhibiting other problems. I've seen other speedometers where the needle simply had been put on in the wrong position, but only on ones where it's easy to open them up (I.E. not BMW's).

There's a small number on the speedometer face that indicates its ratio. Check that and compare it to your differential. There's a chart on Snobum's site that shows you how they are supposed to be matched.
http://bmwmotorcycletech.info/ringgears.htm

[BobW]

Just checked the odometer on an 85 mph airhead. It seems accurate. My oilhead reads 10% high. This is checking on a straight five mile highway with DOT mile markers. I have no idea about speed, but when running in traffic occasionally a car ahead will run at 55 as indicated by my speedo. When the speedo shows 55 or 60 and a car passes at least 15 or more faster, I seriously doubt they are running the limit.
One of the digitals seems like an answer without running a GPS or needing a phone ap. Acewell with BMW adapter looks nice some days. But it costs several tanks of gas and maybe even a cheap tire. It is cheaper than the last ticket I got.
Bob

[Major Softie]

Just checked the odometer on an 85 mph airhead. It seems accurate. My oilhead reads 10% high. This is checking on a straight five mile highway with DOT mile markers. I have no idea about speed, but when running in traffic occasionally a car ahead will run at 55 as indicated by my speedo. When the speedo shows 55 or 60 and a car passes at least 15 or more faster, I seriously doubt they are running the limit.
One of the digitals seems like an answer without running a GPS or needing a phone ap. Acewell with BMW adapter looks nice some days. But it costs several tanks of gas and maybe even a cheap tire. It is cheaper than the last ticket I got.
Bob

The 85 mph speedometers are the exception. The same law that limited speedometers to 85 also required them to be a lot more accurate. When the law was repealed (or time ran out on it), bike speedometers went back to being very optimistic.

[SteveD]

Just checked the odometer on an 85 mph airhead. It seems accurate. My oilhead reads 10% high. This is checking on a straight five mile highway with DOT mile markers. I have no idea about speed, but when running in traffic occasionally a car ahead will run at 55 as indicated by my speedo. When the speedo shows 55 or 60 and a car passes at least 15 or more faster, I seriously doubt they are running the limit.
One of the digitals seems like an answer without running a GPS or needing a phone ap. Acewell with BMW adapter looks nice some days. But it costs several tanks of gas and maybe even a cheap tire. It is cheaper than the last ticket I got.
Bob

The 85 mph speedometers are the exception. The same law that limited speedometers to 85 also required them to be a lot more accurate. When the law was repealed (or time ran out on it), bike speedometers went back to being very optimistic.

I have one of those on my R100RS and it is very close to the speeds a GPS shows. Here in Victoria, Oz, the speed cameras show no favour so having an accurate speedo can save cash. Whilst the BIG numbers are in mph, it also has kmh. After a while it's intuitive as per needle position seen at a quick glance anyhow.

The other option is a bicycle speedo which is cheap and easy and more commonly mentioned before the GPS and expensive digital systems became de rigueur.

[Airbear]

One of the digitals seems like an answer without running a GPS or needing a phone ap. Acewell with BMW adapter looks nice some days. But it costs several tanks of gas and maybe even a cheap tire. It is cheaper than the last ticket I got.
Bob

Bob, I had an Acewell 2853 (cost $250 here in Oz), and was mostly happy with it, except that the LED idiot lights were all but invisible in sunlight, so I had to install proper ones in the headlight bucket. Then it broke a long way from home, so I bought a bicycle computer for $40 as a temporary fix. It's a Cateye Velo 7, and I really like it. It is now a permanent fixture - it is easier to read, has two trip meters and a host of other functions. I need to organise some illumination for night riding, and that is on the list of things to do. Some of the more expensive bicycle speedos have a wireless sender - easier to fit - but I haven't tried one of those. If you go this way, make sure the speedo will register more than 100kph or mph.

[hzbloke]

When I first got my bike the speedo consistently read about 30% fast. When it eventually broke (about 8 years ago) I sent it off to a speedo mob and they corrected it. I never found out how but it was, and still is, fairly accurate. Curiously, when it broke again recently the original mob said they don't do bike speedos anymore.

I tried one of those wireless speedos on my other bike and had no joy at all. It randomly showed random speeds. It turns out that the ignition system was interfering with the signal. That may have been because it has magneto ignition and no suppression at all. The wired one works really well.