Originally Posted by dnrobertson
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".
David, it would be interesting to restrict the top of the airbox back to snorkle size to see if you get a different reading. Like you I have run my BST40 with the side panel off and it made no difference I could notice.
I had a mouse issue with my BMW airhead and 'screened' the intake openings to the airbox.
The motorcycle would not run over 70 mph.