300ex noise

[sprtrx300ex]

On my 01' 300ex there is a deep loud humming noise when i give it about 1/4 - half throttle in every gear, and it seems that i dont get the right amount of speed in each gear.:(

[Ex'r Marlin]

The first thing I would check is the condition of the air filter. I don't know if this would cause the noise you described, but it may if it does not get the required air, and this will definetly hurt your performance and speed. Anyway, better to be safe than sorry. If possible, I would ride your 300ex, then ride a friends 300ex to compare apples to apples.

Good luck!