I made an air box which is chronicled on the tech site under "helmholtz resonator". Here is a picture of the finished box with 2 - 2" elbows connected to 1-1/2" pipes to the front of the bike. It's a little crude, being thin aluminum with lots of Wobbly's rivets, and reinforced with a mat of fiberglass and resin. I dynoed (apparently not an actual word) it last Saturday at NRHS Performance in Longmont with little success. First we ran it several pulls with the top of the airbox off and got 42.5 hp, down about a 1/2 hp from last year. Then we cut the exhaust off from about 29" to 24" because I had lengthened it to get thru my new fairing. We immediately gained 1-1/2 hp to just over 44 hp, which means I'll have to re-route the pipe and modify the exit thru the fairing, but that's doable. Funny thing is that the power curve moved down about 500 rpm from last year. Possibly thru a couple of rebuilds I have changed the lobe centers, which is easy to do with 5 different keyways and three different offset keys for the crank pinion which drives the cam gear. Unfortunately, by this time the entrance spigot to the air box broke loose (but not off) from the airbox. We then put the cover on the airbox and ran another pull. We lost about 5 hp. I then removed the 1-1/2" pipes to the front of the fairing leaving only the 2" elbows and tried again. We only gained back about one hp, so I concluded the airbox was not going to work. Perhaps too small (approx. 5" cubed.) But the good news is that I gained 1-1/2 hp from how I ran at BUB this year. I hope to get more dyno time before next August to try some different intake airhorns and possibly different exhaust combos. Other suggestions are welcome.
Tom