Speedometer pinning at 10 MPH

Hey guys,

Slowly been working on and tinkering with my 79 KZ750. When I bought the bike the bottom of the speedometer cable, where it meets the front hub, had been shaved off and the prongs were completely rounded off. So I ordered a new cable from Amazon (Motion pro 03-0161) and installed it.


What is happening now is the speedometer gets to around 10-15 mph and just flutters but never moves any higher. If it means anything the odometer/trip reader still registers. I found a topic that talked about comparing new and old cables and it actually does look like my cable is about 2 inches shorter than the old one. If I wouldn't of done this comparison I would have never noticed because the cable fits well up against the bike and there is plenty of cable to feed up into the speedo. I attached a picture of this. Could only a few inch difference cause this much of an issue?


I have obviously seen both the front hub gear go bad as well as the speedometers being faulty as well and causing for the needle to flutter but my issue seems much more specific. I would like to just hear the logical way to further diagnose this problem. Is it more common for these "gear box assembly" (part number 41078-008) to go bad? Would it be worth it to pull the part off and clean it up? I have read that the oil or whatever is in the speedometers can leak and corrosion could occur inside but it seems its can be very difficult to get them right.

Let me know what you guys think.

As always I appreciate the help.


Jordan

Take a variable speed drill with a stick or wooden match stick in it, run it in reverse, then tell us what happens. You could also hook up the the bottom of the cable to check if it works.
Steve

Steve knows this but If the OD is turning. then the driven cone hub is being spun by the four pole magnet... there is no mechanical connection between the cable and the actual speedo movement.
Lately I've been seeing some decent deals on eBay for used, working speedos.

Thanks for the help guys. Did some testing and cleaning but with no success. I used the drill method to test the old cable but didn't think to use it for testing the speedo. When I hooked up my corded drill it pegged at the same speed.
Got a new one off eBay for cheap and cleaned it up and everything seems to be good.

Thanks again,

Jordan