cars and motorcycles that meet smog requirements run pretty lean at idle and cruise speeds. but under full throttle [ open loop] they all run a little rich to protect the engine from pre ignition. a full system might lean out some of that rich condition under full throttle, but i doubt enough to hurt the engine.
this is not science but for some reason a less restrictive exhaust system many times does not lean out the idle and low speed A/F ratio. my 04 Z 1000 100 % stock after a full MUZZY lost about 2-3 MPG [ richer]. i am never going to say do not install a PC and do a a/f check. that would be foolish.
but i also feel from 40 years of playing with motorcycles that just a exhaust system will not screw up your engine. if my ZED started running bad SURGE, HESITATE,POOR THROTTLE RESPONCE OR A BIG SWING IN FUEL MILLAGE i would do a PC.
my bike halls ***, gets steady 40 MPG and just has spot on driveability. a
pc is just a tool. some need it some do not. your A/F ratio on a new bike is not close to perfect. lean down low and rich at full throttle. all a PC does on a dyno is lean out the mixture under full throttle to gain some HP nothing more. if a dyno operator leans it out too much to give you a nice HP gain it is more dangerous to your engine than if you left it alone.
this is my 2c worth. if my post makes you think outside the box i am happy.
i have a victory motorcycle also i ran it for 2 years with a very modded exhaust without a PC. it ran fine. it was leaner than stock becouse my fuel millage went up to much. after 2 years i added a S&S air system which really woke up the performance. at that time i had a performance down load put in the computer and it needed it for sure. some bikes you can do a down load to the stock computer which does about the same thing as going to a PC. it re programs the A/F ratio. with a PC you can change the settings. with a down load you can not.
Last edited by notabiker; 12-06-2010 at 03:47 PM.
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