Speedometer Mystery

This may be a long question with contradictory observations, so I'll throw out a short version first, then add the background and details.

Short version: It seems that my speedo needle reads kph, but the odometer reads miles. Am I crazy, or is this even remotely possible?

Long version: Was working on the bike with a buddy today, adressing two issues: speedometer noise (which I thought was the cable), and speedometer accuracy. Pulled the cable out of the outer sheath and lubed it with white lithium grease, noise actually seemed to get louder. Took cable loose from speedo and problem disappeared. Ok, time to open up the speedo.

Opened it up and two small black screws fell out. After an exhaustive search, we could not find any place where they seemed to be missing from. Cleaned and lubed what we could. Of course the ultra-fragile needle broke into multiple pieces during this process, so fabricated another from a toothpick, reassembled and the speedo seemed smoother and quieter than ever. Good deal, time to look into the accuracy.

Had my buddy drive beside me in a car and compare his speedo readings to mine and they're considerable different. For example when his says 50 mine says 32-33. So we're puzzling over this, throwing out ideas, and I happen to notice on my speedo that 50 kph is roughly 33 mph. I'm thinking this is just a coincidence, but just for the hell of it we compare speeds again, this time with me rolling steady at 20, 30, 40, & 50 kph according to my speedo, and they match up either exactly or within 1 with the mph reading on the car speedo. This is way too much of a coincidence, so we look at the gauges further and notice:

1) The face of the speedo looks old and faded, but the face of the tach looks much newer.

2) The face on the tach is held on by two black screws that look very similar to the ones that fell out of the speedo.

3) The face on the speedo is also held on by two black screws, but they look smaller than the others and seem to be glued in.

I had never really thought about metric vs mile speedos and if there was a difference. I guess I thought that the difference would be just the face, i.e. which scale was the larger outer one and which was the smaller inner one. But then it occurred to me that the odometers would need to be different, to either click miles or kilometers, so I reset my trip odo to 0 and travelled exactly 1.0, and the car matched it exactly.

So... is it possible that a previous owner replaced the gauge cluster with another, realized after the fact that it was metric, replaced the face on the new speedo with the face from his old one, somehow lost the original two screws inside the speedo in the process and left them there (wtf?), improvised with two other screws but glued them in, and changed out some odo part so that it clicks kilometers but the needle reads kph? I know, it's ridiculous and I can't make the logic work in my head, but my observations are:

1) The face of the speedo is clearly miles. Mile readings in larger digits on the outer ring, and kilometers in smaller digits on the inner ring. Outer ring goes to 80, inner ring goes to 130.

2) Readings on the inner ring, which should be kph, corresponded almost exactly with mph as read from a car. 20=20, 30=29, 40=40, 50=49.

3) The odo clicks on miles. 1.0 mile as per bike confirmed with same car.

So am I delusional or is this even remotely possible? At least I know I can read the speed from the inner ring and know pretty accurately how fast I'm going. Also, it turns out I'm not quite the wimp I thought I was with respect to speed, I've actually been going a lot faster than I thought I was.

Thanks in advance for your thoughts and comments, even if only to tell me that I'm crazy.

 

The two missing screws are stuck to the magnet that makes the speedo function.

Clich here for more information.

 

biggs, call me stupid but I am totally befuddled by your reply. I don't have two missing screws, I have two extra screws. Are you saying that they stuck to magnet when a previous owner had the speedo apart, and that's why he lost them? Or maybe the magnet is missing two screws, and that's why the speed is not tracking correctly?

I've read thru Fitz's speedo post both before I did this and again just now, but I'm no closer to understanding this.

 

Oops. I mis-read your post.

 

I'll respond when I have some time to type.