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any thoughts on useing one of flowmasters 4-2-1 collectors for an FZ1/R1 engine... It comes in 1.5" inlet and 2.5 outlet...stock header on the FZ1 was 4-1 with an exup valve... The only worry I have is this would be a little wide open and might not be enough back preasure.

I've occasionally wondered if putting one of those "electric cut-out valves" in the exhaust stream with a portion of the butterfly cut off would do much good. .. like an EXUP valve.
If I recall correctly Ferrari did something along that line at the muffler outflow on a few cars.
Audi did on the RS4 for sure but that's a dual exit muffler and they blocked one exit for "stealth mode".

you can always buy a used exhaust from another 1 litre bike.. that is always a good source of tubing and collectors for little money...

For what it's worth, i have a kawasaki Zx1100 motor. I bought a used header from a racer of Legends cars, very cheap. about $45 if i recall. it has a 4-2-1 design. the pipe i'm using is off a stock 1300 cc suzuki and included an EXUP cable operated valve. after much deliberation regarding what to do with the valve, i simply eliminated it. I have carbs not FI. and I have a stage III jet kit. my set up runs fine. i have no issues with back pressure. The engine has a surprisingly good power range and it is not peeky.

see it and hear it at

http://www.youtube.com/watch?v=huW2QyAj3Fg&feature=plcp

I've seen it before and I still laugh. ... knucklehead