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  1. #1
    seaobin's Avatar
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    stutter in the middle

    hey all

    HAPPY EASTER

    went riding yesterday and my 750 was idleing great, and WOT was great and strong, but I felt a stutter in the mid ranges. If cruising around 35-40 it feels like its not right.

    Where should I start looking for an issue. I dont know enough about engine cycle to noodle the issue?


  2. #2
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Sounds to be carb related.

    What throttle position does it seem to occur? RPM really doesn't mean anything to carb Q's.

    Something like 1/4, 3/8, 1/2, or 3/4.

    Reason I say this is because different circuits come into play at different throttle positions, not engine speed.

    1/4 could be low speed jet or pop off

    3/8 may be diaphragm of pop off

    3/4 would be high speed jet

    Have you checked your piston wash for clues?

  3. #3
    seaobin's Avatar
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    I was feeling it around half throttle cruising

    washed looked good last time I checked, but i have not looked today

    carbs were just cleaned and looked pretty good`

  4. #4
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Hmm, 1/2 throttle cruising range.....

    Timing is at full advance at 3000 RPM. It is possible to burn a piston down at this speed if the fuel is inadequate.

    "stutter" sounds like a bog or hesitation.

    First, make sure your elec connections are clean and tight.

    1/2 throttle falls under high speed jet. Did you do any mods to the ski, like F/A's?

  5. #5
    seaobin's Avatar
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    stock FA
    Jets are up 2 sizes due to oil block off
    bored .5 over
    water rail removed and redirected to pissers
    stator replaced last fall due to shorted coil
    plugs look good-- Mocha ish
    had thumb nail wash on all piston crowns

    I will double check compression tomorrow and peek at the pistons

  6. #6
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    2 jets larger on the hi or low?

    Was it always like this and the stutter just started? Or did you block off the pump this winter and this is the first ride since then?

    Next time out, after you verify it isn't running lean first, try to make it happen again.

    Only when it happens, try closing the choke, or give it a shot of fuel with the primer. See if that helps or hurts the problem.

    I'm thinking you're too rich with fuel because of the jets. You prob just needed to open the hi speed screws 1/4 turn for the premix and OS pistons.

  7. #7
    seaobin's Avatar
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    but if too rich would i not have larger wash patterns. finally have it running steady and cool and i dont want to burn it up

  8. #8
    seaobin's Avatar
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    2 sizes up on high 1 up on lows

    as recommended when I did it

  9. #9
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Quote Originally Posted by seaobin View Post
    but if too rich would i not have larger wash patterns.
    Not necessarily.

    The high speed screw adjustment comes into play from 3/4 to WOT.

    With 1 low and 2 hi jets upsized, you're in essence 3 jets over factory.

    You might want to try going down 1 jet size on the hi. And turning the hi speed screw OUT another 1/2 turn to compensate.

    You never answered the Q, though.

    Did this just start happening?

    Or is this from mods done like the overbore and premix, and never dialed in perfect yet?

  10. #10
    seaobin's Avatar
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    I have finally gotten it running well after the bore and rebuild. I don't have lots of time for tinkering right now, so its slow.

    Finally got the cooling issue straightened out and now I cannot be satisfied with anything. Rides great, and is lots of fun, but I am so worried about burning it down again that I am feeling for any possible issue

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