"Tone" sound from engine at 4,500 RPM (650F)

[Human Potato]

Hi Guys,

My 650F has done 2300km and I have only recently noticed that as soon as the engine hits 4500RPM in any gear an annoying "tone" sound comes from the engine (sorta like feedback when you put a microphone next to a speaker).  It only happens exactly at those rpm and goes away anywhere else in the rev-range.

Any idea what would be causing this?  I am worried that the engine has somehow gotten used to running at those rpm and is now "excessively" bedded in at 4500.

[pmackie]

This patch of "raspy" vibration seems to occur on all 600's (and I guess your 650 too). On mine, it occurs from approx 4500 until approx 5000 rpm. Some members have speculated that it is related to the intake cam, but I have no specific data.

Rejetting by shimming the needles, removing the airbox snorkle and adding an aftermarket can decreased the effect somewhat on mine, but it is still there. I've gotten used to it, and hardly notice it any more. My bike now has 53,000 kms with no ill effects.

Don't be concerned.