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Reducing header outlet

Discussion in 'XJ Modifications' started by Nate, Mar 30, 2007.

  1. Nate

    Nate New Member

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    Hi there, I have a 1981 XJ650 with a 4-1 head pipe that has a 2 1/2 inch outlet. I can't find a muffler to fit onto this. So I'm looking for info as to how do you go about reducing the pipe to fit the smaller muffler inlet sizes.
    Would this cause any problems with the bikes performance?
     
  2. bosozoku

    bosozoku Member

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    A better way would be to find a reducer to connect the two pieces. A muffler shop should be able to make one for you.
     
  3. Ease

    Ease Member

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    I had one mad at a local shop (Mineke) for free... Just cut a slit in the pipe where it goes over the header and clamped it on with the clamp from the old slip-on.

    [​IMG]
     
  4. PainterD

    PainterD Active Member

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    They sell the reducers at most muffler shops that will get you what you need. Or slip on a small car muffler just for the hell of it and see what it sounds like! I slipped an old glass pack muffler on my MAC header pipe and it sounded kinda nice, just looked like hell. I think you should be able to reduce the outlet down to 1-1/2" and use just about any kind of muffler (stock or after market, depending on that kind of noise level you want) and you should be in business.
     
  5. Nate

    Nate New Member

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    Thanks, That is what I did. But now that the muffler is on I have very little power below 3500 RPM, as soon as I get past that the bike flys. Do you think I might have to adjust the mixture screws on the carbs? If so What is the safest way to remove the factory installed plugs?
     
  6. bosozoku

    bosozoku Member

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    Let's see now...you've just installed a reducer that has a cross section of about 1.75 square inches, onto a system designed with an outlet size of almost 5 square inches.

    It should be no surprise that the engine won't rev properly.

    No amount of carb-fiddling will remove the effects of the cork in your exhaust.

    Put on a properly sized muffler, or get used to a very hard to ride bike.
     
  7. Nate

    Nate New Member

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    I only reduces it to 2 inches from 2.5 inches for a loss of 1.76 sq.in. It looks just like the picture that Ease has posted. I'm not sure where you came up with the figure of 1.75 sq. in. Now, is it still in your opinion that no amount of fiddling could overcome the lagging at lower RPM's

    Ease, did you have to modify the fuel mix to overcome the reduction of size as in the picture that you posted?
     

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