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What jets for 10 to 1 compression

Discussion in 'Motorcycle Tech Talk' started by c_sdonen, May 17, 2010.

  1. c_sdonen

    c_sdonen Member

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    Have a Evo 80 inch slightly oversized with high compression pistons 10:1, and ported heads with stage 1 air cleaner and exhaust. The recommendation for stage 1 is 46 slow jet and 185 main but that was not for a ported engine or high compression. Does ported heads and higher compression usually require a change in jetting? is so how much would be recommended. This is basically a touring bike that I just wanted to get a little more out of.

    :)
  2. Art_NJr

    Art_NJr New Member

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    The compression ratio is irrelevant to the jetting. And with ported heads, the slow jet normally does not need to be changed, but the main jet size will (probably) need to be increased. By how much? That I can't say for your bike & it would be best to get more than one to trial & error with. In other words, if you're starting with a 185, get a 190 & a 195 - wouldn't hurt to grab a 200 while you're at it.

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