Opened up speedo

[DS74BMW]

I disassembled the instruments today, and found the trip-meter shaft broken [square drive end sheared].

I attached my cordless drill to the speedo and tach, and slowly ran the drill up to max of 1200rpm. The speedo ran perfectly to 68mph, at drill max. The tach did the same to 3000rpm; no wavering from either instrument from zero to these speeds. All the gears, etc looked good, the lube looked good, as well. This leads me to believe I have cable issues, as they are either originals, or replaced a long time ago. I do not know how the cables are driven on the tranny/engine ends, however, and whether or not the drive ends have a problem. The cables seem to work free enough, but a visit with both Rick Borth [Overseas Speedo], and Darryl [Palo Alto Speedo] gave me affirmation that the cables, with age, will cause the symptoms I described, and both could not say how the cables are driven.

I removed the trip-meter cluster, and had to set up in my bench mill to properly remove sheared square drive, so as not to damage the receiving female shaft.

http://i125.photobucket.com/albums/p71/crayquilts/IMG_1729.jpg

Any insights on the possibility that the drive ends of the two cables are a potential issue, would be appreciated. Rick and Darryl both thought a cable-only issue, but don't work on BMW's like the members here.

In any event, I will purchase new cables, just don't know where, yet. Thanks. Richard

[sumran]

It is unlikely that the drive end is problem on the speedo at least. I do not have a mechanical tach, so I can't speak to that one. The speedo is driven by a worm gear off of the output flange of the transmission. Both parts of the gear assembly that drive the cable are substantial and much stronger than the cable.

[DS74BMW]

It is unlikely that the drive end is problem on the speedo at least. I do not have a mechanical tach, so I can't speak to that one. The speedo is driven by a worm gear off of the output flange of the transmission. Both parts of the gear assembly that drive the cable are substantial and much stronger than the cable.

Thankyou, Randy. By saying "substantial", are they steel or nylon, and are they greased or run in oil? I have not been into that system of the engine yet.

Can anyone weigh in on the tach drive?

[sumran]

Thankyou, Randy. By saying "substantial", are they steel or nylon, and are they greased or run in oil? I have not been into that system of the engine yet.

Can anyone weigh in on the tach drive?

Both are steel. They are lubricated with gear oil from the tranny case.

[tvrla]

The drive ends aren't something to concern yourself with. It's the cables.

As for the trip meter, there's an easy fix for that. Drill a hole about the same size as the square end that broke off the knob. Make some square stock the same size as the old, but a 1/4" longer or there-about. I've used a stainless bolt ground down with flatted sides. Heat up the square stock (so it'll melt the plastic as it's inserted) and press into the new hole to the proper depth and you're done!

[DS74BMW]

The drive ends aren't something to concern yourself with. It's the cables.

As for the trip meter, there's an easy fix for that. Drill a hole about the same size as the square end that broke off the knob. Make some square stock the same size as the old, but a 1/4" longer or there-about. I've used a stainless bolt ground down with flatted sides. Heat up the square stock (so it'll melt the plastic as it's inserted) and press into the new hole to the proper depth and you're done!

Glad the drive ends aren't the problem!

Good suggestion for trip meter shaft, I will incorporate that.

Has anyone dealt with Bike Bandit for OEM parts? They list speedo cable for $43.85, and tach cable [w/sq rubber grommet] for $53.58. They show parts schematics/lists/prices for BMW's from 1969 to present.

[sumran]

I purchased an OEM speedometer from them. I have also purchased some Non-BMW stuff. They can be slow on the OEM stuff. I don't think they stock it, so it is dependent on how long it takes them to get it from their source. In general, they have competitive price and good service.

For the cable I would look to sources that specialize in BMW. Here is one possibility.

http://www.bmwhucky.com/

[shire2000]

I get my speedo cables from BenchMarkWorks. Usually pay around $30-$40 for them, plus shipping of under $10. That is way cheaper than what my Canadian BMW dealer wants for one. They want just under $100.

The cable guts, basically twisted steel cable, will break and fray over time. This causes the frayed parts to catch inside the tube covering and will make your speedo bounce all over the place. I am waiting for a cable to arrive ths week for my RT because the speedo is showing that I am going anywhere from 30-70MPH when I am going approx. 50MPH. It has slowly gotten worse over the past year, so figure I better replace it before it breaks altogether. Replacement is very simple, just have to take the tank off and run it thru the holders on the frame top tube down to the back of tranny.

As usual, my personal bike is always the last to get little things like this done.

[DS74BMW]

I get my speedo cables from BenchMarkWorks. Usually pay around $30-$40 for them, plus shipping of under $10. That is way cheaper than what my Canadian BMW dealer wants for one. They want just under $100.

The cable guts, basically twisted steel cable, will break and fray over time. This causes the frayed parts to catch inside the tube covering and will make your speedo bounce all over the place. I am waiting for a cable to arrive ths week for my RT because the speedo is showing that I am going anywhere from 30-70MPH when I am going approx. 50MPH. It has slowly gotten worse over the past year, so figure I better replace it before it breaks altogether. Replacement is very simple, just have to take the tank off and run it thru the holders on the frame top tube down to the back of tranny.

As usual, my personal bike is always the last to get little things like this done.

It appears your speedo doing the same as mine. I didn't want to "crash" my speedometer, so I decided to address this now. I've had my bike a week, and only got to ride it 40 miles - but I do like wrenching, and am enjoying this German engineering.
I just ordered from bmwhucky. The speedo was $42 and the tach was$47, with shipping adding $7.80. These were in stock, and Hans said he would ship today. A very pleasant fellow to deal with. :thumb