As already said a certain amount of that type of noise is normal with these.
The damaged gear happens if the kickstart is engaged accidentally when the engine is running.
Change the idler and check it hasn't transferred marks onto the corresponding gear on the back of the basket.
This happened to mine and did make the noise worse however this noise doesn't go away when you pull the clutch in.
Make sure you use the correct bolt in the clutch centre. (has a hole through it)
Ok so we have a 2010 280 and a 2010 300, both standard bikes.
The 300 appears to weight the front much more, this is noticeable just riding away from standstill.
Can anyone shed any light on chassis differences?