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Thread: Engine Idle 200-300rpm surge

  1. #1

    Engine Idle 200-300rpm surge

    Just did exhaust wrap and paint, oil change to Royal Purple (Crank + Trans), rocker gasket seals, and a very late 10,000 mile service and check with everything well within limits. Before doing the tune up I'd have the odd bog on fast throttle pull. Now on warm up the engine will continually surge it's idle from 900rpm-1300rpm with the odd miss fire. Once warmed up and on the move it's smooth and revs very easily... runs like a champ over the last few weeks but has bogged on hard launch a few times. I've re-checked and adjusted the clutch and throttle cables and performed a TPS reset and idle adjustment by the book and checked and rechecked all the electrical connections atop the engine (from the drop), but the warm up surging continues. I notice when on ECMSpy it will run in Open Loop for idle until it hits a missfire when the Region changes to something too quick to check. Wondering if it's the O2 sensor, but would like some ideas before I drop the engine again. Only 13,250 mi on the bike.

    Any ideas?
    Last edited by LifesHarlequin; 04-18-2016 at 12:24 AM. Reason: added bogging on hard launches

  2. #2
    Senior Member rchuff's Avatar
    Join Date
    Apr 2012
    Willow Grove, Pa
    Have you checked intake manifold gaskets for leakage? Common problem on buells. Easy check just spray carb cleaner around manifold to head and if idle changes you have found the problem. If 02 is taking a long time to go into closed-loop it could be on its way out.
    Last edited by rchuff; 04-18-2016 at 12:55 AM.

  3. #3
    Senior Member Chicknstripn's Avatar
    Join Date
    Aug 2014
    High Point, NC
    You don't have to drop the engine to replace the O2. You can get to it buy disconnecting the lower shock bolt and removing the fan. Isn't the easiest thing to do, but depending on how comfortable you are with an engine rotation, this process definitely has a lot less moving parts.
    Check this thread out:

    Before doing any of that; definitely check those intake seals!

  4. #4
    I've done the shock removal before to replace the rear cooling fan, just had an annoying experience after when the fuel line was chafed and had to be replaced, but definitely willing to do that versus engine rotation. Will check both and report back. Thx for the help

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