Speedometer issue

[DLD1]

Any of you ever have your speedometer start reading faster than you're going? Mine did recently for some reason. It's stable, and the odometer appears to be correct, but it's approximately 10mph fast at around 60 or 70. I've never seen one do this. Any insight?

Thanks,

DLD1

 

[XSLeo]

How long have you been running it? At first it may have been trying to spin in old hard grease. Now after running a bit the grease has softened and provides less resistance to the turning parts inside.
Leo

 

[DLD1]

I've been riding the bike to work almost every day for a couple of years now.

 

[XSLeo]

Hard to say then. That was my best guess.
Leo

 

[DLD1]

Thanks, Leo. It's not a huge problem. I just don't know why it would read high.

 

[retiredgentleman]

Its just because it 30 or more years old. They are actually quite simple inside. A magnet driven from the front wheel causes a metal disk (with indicator needle attached) to rotate. The rotation of the disk/needle is counter balanced by a spiral spring. Your spiral spring seems to have weakened.

On my bike the speedo is accurate, but my tach has started to read about 500 rpm low. So in my case, its likely that my magnet has lost some of its magnetism.

Oh the joys of old motorcycles!

 

[DLD1]

My tach gave out a while back. I took it apart and it was disentigrating, so I had to replace it. I just always expected that the speddo would read slow if it was wearing out, not fast. I've been thinking about getting one of those digital speedo/tach combos. Maybe I'll have to buy myself a Christmas present!

DLD1

 

[pamcopete]

DLD1,

1. First strap your GPS to the bike and verify that the speedo is in fact reading incorectly.
2. Either replace the speedo cable or go to Advance auto and buy a universal speedometer cable repair kit for $6.
3. Take the speedometer drive on the front hub apart and clean / grease it.
4. Forget the speedo and use this spreadsheet to convert your RPM to MPH.

Revs to MPH

 

[DLD1]

Pete,

Thanks, good ideas all.

DLD1