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Mac 4-1 exhaust - rejetting needed?

Discussion in 'XJ Modifications' started by wgul, Jul 24, 2017.

  1. wgul

    wgul Active Member

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    Hey all. After much research here I wasn't able to find out if rejetting will be needed if I get the Mac 4-1 exhaust for my xj650. Mac states that it might not be needed. I'd like to hear some real world experiences with this aftermarket exhaust. I don't think I'd get it if I would need to rejet the carbs. I intend to leave the air filter as stock. I'll just stay with the temp patched stock exhaust until I find another used one in better shape. I appreciate any input on this. Thanks
     
  2. jsngrimm

    jsngrimm Member

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    I do not know for sure, but most likely yes. I know there are some people here with the MAC system that would know
     
  3. Toomanybikes

    Toomanybikes Well-Known Member

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    Did an xj650rj last summer with a Mac exhaust and it did need one size up to a 114 on main jet. Now that is a Canadian bike that started with a 112 main as original main jet so your bike should be a 110 stock jet you may need to go 2 sizes up. Us bikes set up a bit leaner for federal emission standards
     
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  4. wgul

    wgul Active Member

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    Thanks for sharing your experience. I'll have to go stock, which is fine.
     

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