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Surging at cruise speed

Discussion in 'CVP Stage 1 Tuners Kit' started by Peter S, May 6, 2012.

  1. Peter S

    Peter S New Member

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    Hi Ken,
    Installed 45 + 185, needle, emulsion tube and spring on the 1200 Sportster 2005. Stage 1 air and adjustable mufflers (Peacemakers).

    Idle mixture= no effect when adjusting. The engine is idling pretty good on 900 and doesn´t cough or hesitate. I am more interested in the fuel economy.
    Shall I go down to 42 again?

    Very slight "pumping" (revs going up and down a little, maybe some 10-20 rpm)when cruising on 2000 - 2500 rpm and keeping an even speed. Is the spring in the kit softer than original? What else can cause the very irritating "pumping"?

    Open or closed mufflers doesn´t affect above symtoms.

    Peter
    Peter S, May 6, 2012
    #1
  3. hotroadking

    hotroadking Super Moderator Staff Member

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    dang I thought this was gonna be a porn thread...
    hotroadking, May 6, 2012
    #2
  4. kenfuzed

    kenfuzed Administrator Staff Member

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    Hi Peter, the #45 pilot jet should be fine and the original 42 is almost always too lean on a 04-06 XL1200.

    I'm not real familiar with the Peacemaker exhausts other than seeing them at some dealer shows. I would have to believe that anything that can vary the exhaust sound inevitably varies flow, so I would recommend tuning to only one of the exhaust settings.

    The spring is slightly shorter/softer than stock however surging typically isn't a condition of the slide except during deceleration or when the vacuum port hole has been drilled too large (1/8" or larger). I would suspect an intake leak at the manifold boot as this can cause something similar to what you described.
    kenfuzed, May 6, 2012
    #3
  5. Peter S

    Peter S New Member

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    Sorry Hotroadking! I rather have the bike screaming , vibrating and coughing under me than ........... And in the long run it´s much cheaper! :)
    Peter S, May 7, 2012
    #4
  6. JohnnyBiker

    JohnnyBiker Well-Known Member

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    Hey Ken, will a picked diaphragm in the carb cause surging?. Peter, I am assuming that you have had the carb apart yourself and have put it back together?
    JohnnyBiker, May 7, 2012
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  7. Peter S

    Peter S New Member

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    Thank you Ken for changing to "surging" :D
    Peter S, May 7, 2012
    #6
  8. Peter S

    Peter S New Member

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    JohnnyBiker, I managed to change the needle and spring keeping the diaphragm in it´s groove and paying particular attention when replacing the lid so I hope it´s OK.
    I think I read somewhere that a leak, even a minute one, will result in unchanged idling but loss of throttle response? When I firewall the throttle everythings seems normal.
    Peter
    Peter S, May 7, 2012
    #7
  9. JohnnyBiker

    JohnnyBiker Well-Known Member

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    It is still possible that that diaphragm got pinched as you put the cover back on. Have you checked the accel pump diaphragm as well?
    JohnnyBiker, May 7, 2012
    #8
  10. kenfuzed

    kenfuzed Administrator Staff Member

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    I'm still leaning toward the possibility of a vacuum leak.

    If you have a propane torch, turn on the gas (don't light it) and while the bike idles wave the nozzle end around the manifold area. Repeat the test with the rpm's slightly increased. Any intake leak will draw in the gas and be evident by a drop in rpm's.

    The most common place I've seen intake leaks are where the carburetor seats into the rubber manifold boot. Sometimes aftermarket air cleaner assemblies will pull the carb forward and out of the boot just slightly. Applying some clear silicone grease to the inside of the boot will aid in a good seal. I'm not sure about your country but this grease is found here in auto parts stores at the counter sold in single-use packets for use on spark plug wire boots.
    kenfuzed, May 7, 2012
    #9
  11. Peter S

    Peter S New Member

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    Will try the propane method and the silicone grease.

    Back to my question abt. the idle mixture: Since adjusting the mixture is effortless the mixture, I guess, must be too rich. Does it matter then if the screw is all in or 2-3 turns out?
    Peter
    Peter S, May 7, 2012
    #10
  12. kenfuzed

    kenfuzed Administrator Staff Member

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    Sometimes it's difficult to get a sense of where the mixture screw cuts into the idle on Twin Cam and the later Sportster models. When turned in less than 3/4 of a turn you may detect a cough or hesitation when blipping the throttle quickly. This can also be used as a starting point to find the point at which the cough is eliminated, then add 1/8th turn outward to that point.
    kenfuzed, May 7, 2012
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  13. Peter S

    Peter S New Member

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    Maybe the effect of the screw is so subtile that I don´t noticed it. I am used to other engines where a more dramatic change is noticable when you adjust the mixture ratio. Thanks for all help Ken.
    Peter
    Peter S, May 7, 2012
    #12
  14. Peter S

    Peter S New Member

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    An update: Put silicone grease on the rubber boot. Surging gone! :)
    Spent some time with the idle mixture and listened very carefully for changes in revs.
    When fully closed a slight roughness could be heard, tried three turns out and went for a spin. Some coughing when accelerating on 2 gear with closed mufflers. Opened them up and it became slightly worse. Opened mixture abt. 1/8 turn and drove a bit = better. Repeated that for a couple of times adjusting a bit every time. Now the mixture is set to 3 5/8 turn open. No coughing, open or closed mufflers.
    Conclusion: You have to listen really carefully to notice changes when fiddling with the mixture screw and adjustin, driving a bit, adjusting again and so on will most likely end up in a reasonable result.
    Thank you Ken and others for your advice.
    Drive Safe!
    Peter
    Peter S, May 8, 2012
    #13
  15. JohnnyBiker

    JohnnyBiker Well-Known Member

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    does this mean that you aren't going to stick around?
    JohnnyBiker, May 8, 2012
    #14
  16. Peter S

    Peter S New Member

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    Thank you Johnny,
    Of course I´ll be following the discussions on this excellent forum. There are always new things to learn abt. Zen and the Art of Motorcycle Maintenance.
    By the way, anyone from Hilton Head SC on the forum?
    Peter
    Peter S, May 8, 2012
    #15

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