Speedometer gear keeps breaking 84 cb650

[horseman]

Just got a nighthawk 650, and am living it.  Speedometer did not work, so I got and replaced drive gear.  The small tang that drove the cable had sheared off.  90 miles later the same thing happened.  I need a new drive again, but could one of you experienced folks give me some guidance.
cable seems free, and lightly lubricated with a thin oil.  Thanks for any advice, otherwise I am going to check into the speedometer itself for some resistance that could have caused the shearing.

[Brittles]

You need to make sure the "stop" on the speedo drive gear is fully seated against the "stop" on the fork.

You should be able to check for resistance from your speedometer just by inserting the cable and spinning it with your fingers from the bottom.

Good luck and welcome.