I have installed an 39mm FCR on my 2005 640A and also a Air Fuel Ratio meter. The bike was running rich across the board and I couldn't correct it easily, so as part of the tuning process I rode the bike without the side of the filter.
No observable difference in the AFR at all. This is with the snorkel removed and a Staintune muffler.
I also know this is controversial on this board to mention opening the airbox has no affect.
But put me on the fence regarding "opening the airbox".
2005 KTM 640A
dnrobertson screwed with this post 02-08-2013 at 10:21 PM