I recently installed a NOS Kirker (Made for Harley w/HD part number) 2-into-2 exhaust on my '94 EVO FLSTN.

It runs great, but I have noticed that while the front pipe remains shiny out of the head, the rear pipe has blued quite a bit. If you put your hand over the exhaust, it seems to pop evenly and there doesn't seem to be a temperature differential.

Any comments?

Thanks!

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This is a often asked question and the answer will be the same, there are only a few things that make the pipe turn colors. First is incorrect fuel ratio's, too lean the mixture takes longer to burn so it continues to burn in the pipe, if the mixture is too rich it takes longer to burn all the fuel so it continues to burn in the pipe. Timing too far retarded will increase the cylinder temp and also not burn all the mixture in the cylinder which again burns in the pipe, lastly an exhaust leak will discolor pipes. Reading plugs, dyno testing are the only two ways I know to see if it is too lean or too rich. Of course replacing the gaskets in the exhaust port will take care of an exhaust leak. Checking the ignition modual, VOES, vacuum leak, and timing will see if the enging is running too far retarded.

Good luck
Doc