While at a stop and in first gear, my 2009 Ninja 250 will shoot up to around 4000 RPM and stay there. It isn't until I let the clutch out a bit (engaging the clutch a bit), it drops down back to 2000 RPM. I've even shifted into neutral while it is revving high and it stays stuck there.

What could be the issue possibly? I've searched "sticking throttle" but that's not really what's happening.

TIA!