Speedometer needle snapped - now miscalibrated

[lauripalokangas]

The speedometer lost its mind the other day, and in the process, broke its needle from the stem. I didn't see it happening, I just noticed at some point in cruising that the needle was gone and the stem didn't know which way to point at. Also, one screw of the face detached from the body and the face hung loose inside the case from only one screw. As I heard lamentatious whining from the speedo, I already ordered a new cable.

I dismantled the speedometer, found the loose screw, and the rest of the needle. The face is now in place, and what is left of needle, glued on the stem. All the gearing looks okay and visually everything works fine.

There are two challenges.

Because the needle is shorter than before, it doesn't reach the stopping (the pin at zero kilometers per hour reading) and can go below zero. Is it essential for the calibration of the needle to rest against the pin at zero for it to stay calibrated? Now the calibration of the needle is off, and the needle points to the 6:30 o'clock while resting.

Also, it seems like an impossible job to find spare needles anywhere. The part isn't listed separately in the parts catalog (ETK). Where would you begin hunting for one? I found a restored speedo for 350 euros, but it sounds like a lot of money for a needle...

The bike is 1979 BMW R45.

Edit: I'm not sure if it's only a matter of calibration. Today during the riding, half of the time speedo showed about 50 km/h, half of the time 180 km/h. At one point it went into hibernation, and woke up after 10 minutes. Odometer and trip work normally.

Edit 2: It's water under the bridge. I found a used speedometer in ebay and won the auction. 🎉

[Barry]

Is it essential for the calibration of the needle to rest against the pin at zero for it to stay calibrated? Now the calibration of the needle is off, and the needle points to the 6:30 o'clock while resting.

I would say not. Having had my speedo to bits you have to lift the needle over the pin and find it's resting position to find a reference before removing the needle to get the face plate off.  Unless you are attempting correct a speedo error the needle is replaced in the same reference mark at the  resting position.

However I think that is only part of your problem.  I suspect the pin on the speed cup has worn or broken allowing the speed cup and needle to be driven violently around  breaking off the tip of the needle. The speedo probably needs expert repair.





 

[lauripalokangas]

The speedo probably needs expert repair.

Thanks for the reply and for the insights. I've bid on a used speedo that would also have the right W-number for my final drive. In any case, the current speedo probably gives ample entertainment for darker winter evenings.

[Barry]

I should have mentioned that the reason In had my speedo apart was to fix what is a common problem with Airhead speedos. A pot metal gear wheel begins to slip on it's shaft such that the odo meter ceases to record the miles or at best records insufficient miles. It's not related to your problem but it's something to consider looking into if either buying a replacement or attempting  to repair the one you have.  Lots of coverage of this problem on all the airhead forums including this one.

[georgesgiralt]

Hello,
As Barry pointed out, IMHO, the cup where the magnet stays is the culprit. And it cans be a small peckle of steel aving found it's place in here and coupling mechanically the two parts insted of a magnetic one.

[Barry]

This the speed cup we are referring to

[Justin B.]

I'm late to the party as I've been up in the mountains for the past few months, but...  On my '57 Chevy the speedometer needle was busted off so I fabricated one from a toothpick that was the correct length, sanded it flat on one side, glued it to the stub, and painted it white.  This was about 20 years ago and it is still in place and working fine.

Justin B.

[skippyc]

I'm late to the party as I've been up in the mountains for the past few months, but...  On my '57 Chevy the speedometer needle was busted off so I fabricated one from a toothpick that was the correct length, sanded it flat on one side, glued it to the stub, and painted it white.  This was about 20 years ago and it is still in place and working fine.

Justin B.
It's this type of ingenuity that is missing in our modern world.