Stock MPG's

Discussion in 'Dyna Models' started by Kwajite, Oct 17, 2008.

  1. Kwajite

    Kwajite New Member

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    I just bought a used 1998 FXDS-Con. It came with thunderheaders and it is loud. He also gave me the stock head pipes and mufflers. I went on a ride today and averaged about 50 MPG. If I put the stock pipes and mufflers back on would my MPG's go down or stay the same? If I keep the thunderheader on the bike I will have to rejet the carb I'm getting a lot of snap crackel and pop out of the exhaust during de-ecel (running lean). If I do that mod will my MPG's decrease or stay the same? I'm trying to cut down on the noise and still maintain good MPG's Thanks for any help on this.
     
  2. Bud White

    Bud White Well-Known Member Retired Moderators

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    Jetted properly it will lose some MPG but not much better fuel loss than melting it down because its to lean .. if it wasnt rejetted for the thunder headers you could put stock back on and most likely be fine
     
  3. glider

    glider Veteran Member

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    It should have been rejetted with the installation of the T Header which would be a rich jetting with the stock pipes. If you are going back to stock, replace the stock jets. They will be listed on the first page of your factory manual in the carb section.
    50 MPG sounds high for a rejetted engine with T Header
     
  4. Kwajite

    Kwajite New Member

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    Thanks for the replys. I don't think the carb has been rejetted for the pipes. When I picked up the bike last week I asked if the carb was modified and he told me no it hasn't. I also saw that the plug is still installed in the mixture screw. So if I go back to the stock system will I loose my MPG's? I do plan on removing the plug so I can get adjust the mixture screw.
     
  5. glider

    glider Veteran Member

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    With the stock jetting and the aftermarket pipes, you are running lean. If you readjust the carb mixture to increase fuel to the engine, the MPG may go down a bit but I would rather have a proper running engine than a high MPG figure any day.
     
  6. nramike

    nramike Member

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    I have a 98 FXD with SE II's and other wise stock {previous owner and dealer records say no carb mods}. I only get about 40mpg. This is mainly highway and I don't ride it hard.