91 K75s Speedo not working

[Joe_t]

I have followed all the suggestions related to this problem as regards the speedo housing itself (taking apart housing, checking for corrosion, cleaning all the posts, etc.) and have come up dry. Last night I took apart the accuator that is housed in the rear end that sends a signal (I presume) to the digital connection at the speedo needle and moves the needle and odometer as the miles pass.

When I took the fitting out of the housing I looked inside and easily moved what looked like a slotted ring. From what I have read this connection between the actuator and the spinning drive shaft could restore the power to the electronics that move the needle.

Comments and suggestions please...

JT

[bmwmick]

Joe,
That "slotted ring" is the pulse wheel that tells the speedometer/odometer how fast the rear wheel is spinning. To test your electronics, turn the ignition on with the bike NOT running. Hold a soldering gun(or any 60Cycle transformer) near the transducer. The Speedo should register somewhere near 45MPH.
If that works, your electronics are good. Since you KNOW the pulse wheel is loose on the final drive carrier, you could try hitting it lightly with a center punch at 4 places around the ring. This ring 'should' be an interferrence fit on the final drive carrier but sometimes they came loose. Don't tap it hard enough to shatter it, just enough to get it to 'grab' the carrier surface.


Keep us posted.

[deilenberger]

Joe,
That "slotted ring" is the pulse wheel that tells the speedometer/odometer how fast the rear wheel is spinning. To test your electronics, turn the ignition on with the bike NOT running. Hold a soldering gun(or any 60Cycle transformer) near the transducer. The Speedo should register somewhere near 45MPH.
If that works, your electronics are good. Since you KNOW the pulse wheel is loose on the final drive carrier, you could try hitting it lightly with a center punch at 4 places around the ring. This ring 'should' be an interferrence fit on the final drive carrier but sometimes they came loose. Don't tap it hard enough to shatter it, just enough to get it to 'grab' the carrier surface.


Keep us posted.

IIRC - the ring is glued to the big gear - and the glue has been known to come off.

People have repaired this by using some epoxy (has to be temperature and oil resistant - JB Weld comes to mind) to reattach the ring to the gear.

If in doubt about your ability to do this job - I'd suggest removing the rear drive yourself, and taking it to a dealer. Bring some epoxy for them also.

[bmwmick]

IIRC - the ring is glued to the big gear - and the glue has been known to come off.

Thanks Don,
I always thought they were 'shrunk' onto the final drive carrier.
(the older I get, the more I learn) :) :stick

[Joe_t]

Hi Bmwmick:

It sounds like I will have to take the drive shaft apart to do either the tapping or epoxy as suggested by Don Eilenberger. Is this a job for a qualified mechanic or can a mechanically inclined but inexperienced guy like me tackle it?

I want to ride this machine not spend days looking at parts on the floor of my garage. Any help is appreciated.

JT

Joe,
That "slotted ring" is the pulse wheel that tells the speedometer/odometer how fast the rear wheel is spinning. To test your electronics, turn the ignition on with the bike NOT running. Hold a soldering gun(or any 60Cycle transformer) near the transducer. The Speedo should register somewhere near 45MPH.
If that works, your electronics are good. Since you KNOW the pulse wheel is loose on the final drive carrier, you could try hitting it lightly with a center punch at 4 places around the ring. This ring 'should' be an interferrence fit on the final drive carrier but sometimes they came loose. Don't tap it hard enough to shatter it, just enough to get it to 'grab' the carrier surface.

Keep us posted.

[bmwmick]

Joe,
You will save 'some' of the cost by removing the final drive and taking it to a dealer to repair like Don suggested.

[breyfogle]

If your level of mechanical confidence includes removing the rear wheel, removing the final drive is trivial. Basically, remove the rear wheel (4 bolts), disconnect the lower rear shock bolt and the rear brake caliper. The final drive is held on with 4 bolts. After removing the FD bolts, the FD simply slips off the drive shaft. No special tools or experience needed.