Trip Odometer Repair
By Fred Scott
You’re resetting the trip odometer, but one of those damned digits refuses to reset properly, so you wind up with three zeros and some other number. A good hint that you have this problem is that the problem digit will advance a little bit with every full rotation of the reset knob. If you’re lucky and gentle enough, you might just get the bad digit to reset to 0.
Other than the reset problem, the trip odometer works normally.
Rest assured, the problem can be fixed with little difficulty. You will need the following items.
- #2 phillips screwdriver
- 3/16″ flat blade screwdriver
(If you think that all phillips or flat screwdrivers are the same, please stop now and send your instrument cluster to a professional)
- One dentist’s pick, available at good auto part stores or Home Depot
Another K bike instrument cluster, or a good tumbler to replace your stuck one. The tumblers, as far as I know, aren’t sold separately from BMW, so you’ll need to try the used market.
We’ll get to identifying a good tumbler in a moment.
- Remove the back cover of the instrument cluster. Be sure to not tear the gasket.
- Unscrew the two phillips screws in the bottom center of the cluster.
- Unscrew the two black slotted screws near the bottom corners of the cluster.
- Unscrew two more black slotted screws in the top right of the cluster.
Now you should be able to remove the center part of the cluster, as well as all of the printed circuit and lights. Don’t force it, if it hangs up, you either missed a screw or need to work a connector loose.
Now you can remove the speedometer. Unscrew the two phillips screws holding it in place, one on the bottom center and one on the far right.
Pull the odometer reset knob to the right, and then lift the speedometer out of the housing.
Looking up into the bottom of the speedometer, you’ll see the odometer assembly. It is held in place by two brass colored slotted screws. Remove these and you can pull the odometer out of the speedometer assembly.
The tumblers are on a metal shaft which has a snap ring at each end. Use the dental pick to remove the right hand snap ring. Be sure that you don’t lose the snap ring. If you do, you’ll NEVER find it again. NEVER!
WIth that done, slide the shaft slowly to the right. If it hangs up, rotate the white tumbler until the shaft slides freely again. Remove the white tumbler. Repeat to remove the Miles tumbler, rotating it if the shaft hangs up. Repeat to remove the Tens and Hundreds tumblers. Finally, slide off the black disk that should be the only thing left on the shaft.
Look in the center hole of each tumbler, and you’ll see a small metal tab projecting into the hole. This is the end of a small spring. This spring engages the oddly shaped groove on the shaft, but only in one direction. This lets the tumblers turn freely as you ride, but locks them to the shaft when you twist the reset knob. This is also why turning the reset knob backwards does nothing. And lastly, this spring is what was hanging up on the groove on the end of the shaft. If you’d gotten stupid and yanked the shaft out (you didn’t, did you?) you would have done damage to the spring. In fact, I suspect that it is an assembly failure of this sort that causes these springs to fail. Mine showed signs of it.
Use the dental pick to feel the movement of each tumbler’s spring. You’ll find that the bad tumbler’s spring is significantly weaker. This weak spring won’t always catch the groove in the shaft, so the tumbler doesn’t reset properly. Occasionally, it’ll get a good grip and will reset.
The tumblers cannot be serviced, so install your replacement tumbler(s) onto the shaft, making sure that the spring is lined up with the groove in the shaft as each one goes on. Install the Hundreds tumbler, then slide its white plastic gear into place. Repeat for Tens, Ones and Tenths.
At this point, test your trip odometer by scrambling the numbers by hand and then twisting the shaft to reset them.
Reassemble the cluster by reversing the above steps.
One last note. I didn’t have a spare tumbler, so I lubricated the bad tumbler’s spring with a penetrating oil, making sure to wipe up all the excess. This wasn’t a permanent fix, but it did make a major difference. As of this writing, I haven’t road tested this fix yet. I also moved the offending tumbler to the One’s position, so that if it does fail to reset, it won’t throw me off by more than ten miles.
That’s all. Hopefully this will help you.
Copyright 2005 Fred Scott