A forum for owners of Yamaha TTR250 trail and enduro bikes!

I was hoping someone a little better informed would answer but, just to help things along, my understanding is that it is a resonator chamber to help even out the air flow to the carb.

There was a thread about these either on here or on the old Yahoo Group but I can't find it 

Mr Yamaha isn't known for spending money on unnecessary gubbins so there is a view that it's best to leave it on.....

I know there are different opinions on carb removal but my view is that it is quicker to remove the airbox altogether (two 12mm and three 10mm bolts) than to leave it in place and try and lever the carb out and possibly damage the expensive-to-replace inlet stub.

Brian