by swtuggle » 07 Jun 2013 15:49
I "deflowered" my airbox early last year. Took a few more months to get the jetting right, in concert with the 26" reverse cones. The head pipes are still stock with the trombone slide underneath. EV, I remember you saying you only had to enlarge the mains on your 350, however after freeing the intake and exhaust, my 501 was still lean all throughout. Ultimately, I very happily settled on 53 idle/pilots, X6 needles pulled all the way up in 50 slides, 268T atomizer, and 132 mains in the PHBH28BS.
I had briefly thought about opening the mains even further to keep it pulling hard up to the redline (8500), but it doesn't act like it's leaning out and surging or missing, it just doesn't continue pulling as strongly as it does up to 7500. I've only witnessed this in the higher gears on an open road, where I have the time and attention to study the tach and the speed of its sweep. In the lowest two gears especially, it sweeps too quickly to accurately see what's happening. It may easily go to red and beyond in first and second, but I don't want to push it and break anything on a bike that's one or maybe three of its kind in a 500-plus-mile radius.
I have two guesses:
First is the cam. If my Ducati-ignited 501 truly has a 500 cam, its specs are relatively mild. A couple of tests I've found from the '81-'82 timeframe showed the 500's peak HP occurring around 7500.
Second are the 26" silencers. They have a considerably larger ID, and are lightweight. They are baffled though, emitting a wonderful exhaust note, fairly deep, but not very loud, unlike the booming 17" repackable straight-throughs. The 26" reverse cones are sealed, so I have no way of inspecting the baffle design. The exhaust pulses at idle feel fairly soft at the outlet, denoting the reduced pressure. What I don't know is its flow at high rpms. Since they are cheap, I'm sure the baffle plates/tubes cause the exhaust to make several 90 or 180 degree turns.
So, if the motor's soft top end is due to the silencers, it's not worth trading to irritating, deafening noise for a few extra rpm I'll rarely ever appreciate.