Georgiadigger wrote on 03/31/12 at 23:52:47:Can you drill holes in the right side of air box to help air flow or does this hinder flow from under the seat? Would I have to rejet the carb if I created more air flow? I just bought a 2007 S40, it backfires very little. I was thinking of blocking flow from under seat and building a air dam from the side. Any thoughts would be appreciated.
Respectfully, Rocky
I had had my carb rejetted with the view to replace the standard airbox with a large (4-5") K&N filter scrounged from a scrapyard.
Unfortunately I could not source a piece of rubber tubing that was the correct diameter AND had the correct 90°angle I needed to go from the carb to the filter, which I wanted flat on the right side, under my thigh.
As was on my very first bike, a Ducati 450cc Scrambler (see red can below seat)
So, there I was with an overly rich mixture and no time to go back to the mechanic. What to do ?
I drilled a number of 8mm (1/4" or 5/16") holes on the side of the REAR half of the airbox.
Why only the rear half? Because the front half is there for looks only.
Air/Fuel Mixture improved, but not so much as not to foul plug.
Have a new airbox cover now, and have (finally) rejetted the bike, will let you know how she behaves.