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Porting?

Discussion in 'XJ Modifications' started by Colin 85 700, Apr 7, 2019.

  1. Colin 85 700

    Colin 85 700 Active Member

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    anyone here ever "port and polish" an xj 700?
    Is it worth it or do the heads flow well enough stock to not care?
    Note: im running headder with pods already, jetted right.
     
  2. k-moe

    k-moe Pie, Bacon, Burbon. Moderator Premium Member

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    Yamaha did a great job in getting everything smooth-enough and mated up well. Not worth the bother IMO.
    Polishing is not exactly the best way to increase flow anyway. Setting up eddies along the surface does a better job, so micro-shot peening is the thing (or was the last time I looked into it).
     
  3. Simmy

    Simmy Well-Known Member

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    Degreeing your cams is probably better money spent.
    I admit I paid a performance shop to do my 911-X.
    He machined slotted holes in the cam sprockets which enables several degrees adjustment of each cam.
    I can't tell you what degrees for inlet and outlet are best, I wanted midrange for sidecar duty.
    Apparently manufacturing tolerances sometimes deliver a motor several degrees out from what the manufacturer intended.
    You can see the adjustment he made by where the bolt is tightened in the slotted hole on the sprocket.
     
  4. Colin 85 700

    Colin 85 700 Active Member

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    Thanks k moe, and yr right, micro shot peen is the new thing.
    A true port polish is/can be better than micro peening, however its very time consuming to do right, and a poor polish job is barley better than original rough cast, unless its real rough, lol! why they use it, qiuck and effective.
    I figured that the yamaha fliwed pretty good, the ports look good, just wondering if there was a speed secret there... Like taking the "recirculation bump" out of a ford big block intake... I can elaborate if anyone cares.. Lol! ;)
     
  5. Polock

    Polock Well-Known Member

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    i had a good size ridge where the intake met the head, smoothed it down with a Dremel.
    that was probably good for 20Hp :)
     
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  6. XJ550H

    XJ550H Well-Known Member Premium Member

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    What jetting are you using?
    can you elaborate on your exhaust?
     
  7. Colin 85 700

    Colin 85 700 Active Member

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  8. Colin 85 700

    Colin 85 700 Active Member

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    image.jpeg
    4:1 2 1/4 collector, 1 7/8 tip with pods.
     
    XJ550H likes this.
  9. JeffK

    JeffK Well-Known Member

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    I love it Polock<LMAO>.......it wasn't lost on all.......

    Colin.....there isn't enough there to go after, plain & simple. Best advice when I left roadracing and began to try to reinvent each bike was to enjoy a bike for what it is. Some bikes like my two strokes, lend themselves very well to mods, often doubling stock power and to some extent, I'm able to get a substantial bump in my turbo with a couple of subtle inexpensive mods but IMHO.... in general, the 700's don't have a lot of overhead to be gained by extensive mods...sticking with the pipe/jet mods might be best bang/buck.

    jeff
     
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