The tachometer on my '09 ninja 250 started to show higher RPMs than it used to. The idle RPM went from ~1500 to ~3000. In fact, RPMs seems to have doubled. Now I rev often to the red line before I feel the bike is ready for an up shift.

The engine is either actually reaching the higher RPMs, or the tachometer is wrong. I believe the tachometer is inaccurate, because by my previous experience, the engine doesn't sound like it's revving as high as the tachometer displays.

Anyone have any suggestions?

Trying to think how it could have happened, I remember that right before I noticed this, I stalled the bike on a traffic light, and started the engine again without the clutch being fully pulled in. Could that have changed anything?

Thanks for any insights!