86 Venture Speedometer goofed up

[86venturejay]

OK guys so I'm feeling a little dumb here. I started hearing this screeching noise at random times and I thought it was my cooling fan. Sooooooooo..... After taking off the radiator and removing the fan, cleaning and lubing all that I could and reasmbled everything, who knew the problem would still exist.

 

Shortly after this, the spedometer started jumping all over the place and I found the problem was the speedometer. Ive got it off the bike and I've lubed it up. Unfortunately, I think I may be to late. I found lots of metal shavings inside and once I hooked everything back up, my odometer works great but the spedometer does not move at all.

 

Can anyone shed some light on how this thing operates exactly? I'm not sure how it works and am wondering if something in there got ground off or something. As far as I can see, it all still seems to be there as as I mentioned, After lubing it up, the noise is gone and the odometer rolls over fine.

 

Any help would be much appreciated. Thanks!!!!

 

Jay:D

[frankd]

I don't have a Venture speedometer in front of me, but this is how all analog speedometers work. The speedometer cable connects to a steel cup. It spins close to but not touching a magnet. The magnet is connected to the speedometer indicator (needle) as is a linear coill spring. When the steel cup spins, eddy current is induced in it (because of the magnetic field) and force is applied to the magnet that applies a force that is linear to speed. The force that is induced pushes the indicator in the direction of rotation, or upscale. The coil spring pushes the needle downscale. Say your going 10 mph. The cup is spinning pushing the needle upscale, and the coil spring is pushing the needle downscale---they balance @ 10 on the speedometer face. When you speed up to 20 mph, the eddy current induced doubles, which douibles the force applied to the magnet. That pushes the needle upscale, and the spring gets wound tighter. They balance each other @ 20 on the scale.

 

The magnet to cup distance can't change or the amount of eddy current induced (and therefore the force applied) will be changed. If the metal chips you found are from the cup pivot bushing, wear would change the distance between the cup and magnet, effecting the accuracy of the speedometer. Also, the needle has to move smoothly, and can't bind anywhere. If it binds, the needle may not move. If you had chips in your speedometer, it may be time for another speedometer. On my 83, I used motorcycle chain lube on the cup pivots, and it stopped the noise and it's still working @ 150K. What I liked about chain lube is that it's thin when applied, then the thinner evaporates and it gets thicker and stays put.

 

Frank D.

[Condor]

Where did you find the shavings?? Inside, or where the speedo cable screws on?? Anyway if your speedo is fubar, I think I have another stashed somewhere. I'll send you a PM if I find it.

[bongobobny]

Yah! Frank has it right! The cable spins a magnet which makes that "cup" move making the needle move. (condensed version) You may have metal shavings jamming up the needle movement or possibly, the needle is behind the stop peg instead of in front of the stop peg, that would prevent the needle from moving as well!

 

You may end up having to replace the speedometer assembly. Good news is all VR's, MK1 and MK2 will work.

 

BTW here in this site we consider the MK1 and MK2 to be a 1st generation Venture, and the RSV to be the 2nd gen. I am not criticizing, happens all the time, but you may get better response to your questions in the 1st gen forum. But as you see, they will get answered even in the wrong forum. we are not fussy here!

[86venturejay]

Frank, Thanks so much for all that info, what I'm looking at in here makes so much more sense now.... lol.

 

Condor, the shavings were found inside, not where the cable screws on. Also upon further inspection and from Franks explanation, I see the problem now. The cup and needle have separated. The shavings found may have been from whatever kept them together. Who knows. PM me and we'll talk about your other speedometer. It would be great if you had one. Just let me know what you would want for it.

 

Bongobobny, Thanks for letting me know my error. I really wasn't sure how to know what mine was so I took a shot! lol... figured I had a 50-50 shot at not looking totally ignorant... hahah... never works out.. haha! Anyway, Thanks for letting me know!

 

Thanks again guys for all the help!

[Condor]

 

Condor, the shavings were found inside, not where the cable screws on. Also upon further inspection and from Franks explanation, I see the problem now. The cup and needle have separated. The shavings found may have been from whatever kept them together. Who knows. PM me and we'll talk about your other speedometer. It would be great if you had one. Just let me know what you would want for it.

 

False alarm Jay. I had a box of stuff from a dash that I had dismantled, and I did find the tach etc.... but no speedo. I must have sent it to someone else??? Sorry. Maybe somebody on the board has one laying around??