Speedometer question

[GregR]

The speedometer needle on my 1983 Venture Royale is sticking. When I purchased the bike the speedometer inner cable had been removed by the owner. He said the last time he rode it the speedometer stuck and his mechanic told him to remove the cable to prevent any internal damage. He bought another bike and put the Venture up for sale and never had the speedometer fixed. I removed the speedometer today and everything appears intact to my untrained eye. I can moved the needle back to zero and it will spring back to 90 mph as soon as I let it go. It is in remarkably good and clean condition on the inside. Hate to just buy a used working speedometer from ebay if there is anything to be done to fix this one. Any ideas on what the problem could be? I hate to just replace a perfectly good looking instrument.http://i120.photobucket.com/albums/o196/TSM01/IMAG0134.jpg

[GregR]

Speedometer is back in. Oiled and cleaned. Needle is not working but at least the odometer and trip meter are still working and I can still track mileage and I'm still confident of the total mileage on the bike. I can judge my speeds by the tach so that's not a big deal I'll just have to live with no mph indicator. There are worse things .

[Kirby]

So that's how the 1st Gen appear to be so fast. Man, they're fast even sitting still. I knew the 2nd Gen's speedometer was 5-7% fast but this is rediculous!

 

:crackup:

[MiCarl]

Wish I'd seen this before you put it back together.

 

Speedometer pointer will tun on the shaft. It's possible it may just need to be rotated to the proper position. Determining the proper position is the tricky part.

[GregR]

Hi Micarl. I was able to get the pointer back to zero. Everything inside the unit seems to be turning as it should so I'm at a loss as to why it isn't moving the pointer. The spring is in place and there is tension on the pointer. I'll ride with it like this over the winter and next summer I definitely plan on making one of the maintenance day events and maybe someone can give me some pointers. I learned a few things about taking the windshield and instrument panel off and got to have a better look at the wiring and instruments in general. So, it was a worthwhile project. I didn't fix anything that was broken AND I didn't break anything that was working. So it was a good learning experience.

[MiCarl]

From your description I can't understand why the needle doesn't move.

 

The cable comes in and drives a worm gear. The worm gear runs the odometers. Assuming the odometers are working then the worn gear is turning.

 

On the end of the worm gear is a magnet. It rotates inside an aluminum cup causing an eddy current. The magnetic field from the eddy current tends to drag the cup along with the rotating magnet. There is a shaft on the cup with the pointer on the end and a spring that resists the rotating of the cup. As you speed up there is more torque supplied, the spring gives and the needle turns.

 

One obvious reason for the needle not to move is the bearings on the shaft are dirty. From your description though it sounded like it would bounce back to 90 after you moved it by hand - doesn't sound like the bearings are stuck.

 

Picture for your reference:

http://media.web.britannica.com/eb-media/77/62777-004-3B9B55B0.gif

On your speedometer the worm gear that drives the odometers is cut into the part labeled "shaft" in the drawing.

[GregR]

Odometer and trip meter are both working. After looking at your diagram it seems to me that maybe the magnet isn't turning which means it isn't building up the eddy current. I can turn the cup and the needle moves. I'll have to pull the speedometer out again tomorrow. There really is nothing to it and as your diagram shows there are only a small number of parts.

[KIC]

If you need any parts, I have an old speedo out of one of my 84 parts bikes laying in the garage. Like they .." If the part fits, you can have it" .. or something like that..