Topic: 81 cb650c rejetting for dual K&N air filters and 2 into 1 exhaust pipes

[dannyrichard]

Hey everyone. I'm at a crossroads when it comes to my 81 cb650c cafe project. It was a stock cb650c with only 13,000 miles but the 4 into 4 exhaust was completely rusted where the headers meet the thinner metal for the mufflers and luckily the person I bought the bike from included some 2 into 1's exhaust. I welded the new 2 into 1's onto my headers and decided to remove the stock air box in place of a pair of oval k&n air filters. (Shock and awe, you idiot, use the stock airbox, step 1 put back on the stock air box). I know I know. If it was simply function over look I'd have kept the stock airbox but for one it's a pain in the ass putting on and off and I am doing some major frame modifications so it has to go. My questions are, by changing my air filter and exhaust on this 81 cb650c, will I be looking at going higher in jets or lower? Has anyone had this type of configuration before (k&n pods and a two into 1 exhaust system)? If so, how far did you go with your rejetting?

[SOHC4 Cafe Racer Fan]

Danny,

Dave Barbier (http://forums.sohc4.net/index.php/topic,140833.0.html) and I are both in the process of builds with 650 engines in 550 frames.  I imagine that Dave will be using some sort of aftermarket air filter (K&Ns or a modified box) because the stock 650 box will not fit into the 550 frame space.  Dave and I are going to run Dynoman's 674 kit, ported head and a Hindle 4-2-1 exhaust, so any numbers we get on jets will not completely mesh with your stock motor, but may help with some feedback on intake filters.  I am still a long way off from firing, since I am only rebuilding a motor, while Dave has a complete bike built and is rebuilding the motor to install into the finished bike.