My tach is spazzing out

[ponchopirate]

So I've noticed that once I go above ~65mph my tachometer goes back and forth about 1000rpms but seemingly only in 6th gear.  The bike isn't behaving any differently at these speeds, the tach is just weird.  I was wondering if anyone has heard of this/what I should do.  Also, I know it's pretty much unrelated but the last time I changed my tires my speedo looked damaged where it connected with the wheel.  Sure enough I discovered it's over shooting about 15mph (saying I'm doing 80 when I'm only going 65).  I know there's about a 10% error but this seems ridiculous.  Anyhow, any help would be appreciated.  Thanks.

[average]

Maybe the cable is loose or needs to be replaced?

[TR]

Also lub it.

[davipu]

it sounds like your cable whare it goes into the motor isn't in the slot. it's like a standard screwdriver, and if you tighten it down whin it's misaligned it will slip at speed.

[ponchopirate]

Thanks for the advice.  I'm off to check it out right now.

[Chuck]

Let us know if that fixed it.  I have this problem too, but I'm just too lazy to ask about it or look into it myself.