RPM drop in while sitting in neutral



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Thread: RPM drop in while sitting in neutral

  1. #1

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    RPM drop in while sitting in neutral

    Hi guys,
    I was sitting at a red light on my way home from a ride this evening (still very hot out around 8pm) and my RPMs would drop and come back up. It did this about 3 times in 1 minute. The bike did not stall, but it quickly dropped and then came back up. My idle is set to around 1300rpm at idle. Maybe increasing the idle to 1600 or so would solve the issue? This is the first time I have taken the bike out in this heat, so maybe that is a factor... But it was at 95f so it wasn't over heating or anything.
    Guy that sold me the bike (original owner) said he's never had this happen to him, and he also never rode when it was 30c+ outside.
    Is this a sign of future problems? This is my first super sport and also the first time this has hapenned to me.
    It is a 2009 zx6r with 25,000kms.
    Thanks!

  2. #2
    JavaFan's Avatar
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    Re: RPM drop in while sitting in neutral

    ...................

  3. #3

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    Re: RPM drop in while sitting in neutral

    The owner manual says 1300rpm idle so that's what it's set at. Maybe when the fan kicks in it causes the rpm to drop for a quick second? I honestly can't tell when the fan is on because my bike is so damn loud LOL
    Why did u change ur post Java fan?

  4. #4
    JavaFan's Avatar
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    Re: RPM drop in while sitting in neutral

    too much opinion
    and not enough reading

    I'm out brother....good luck

  5. #5

    Re: RPM drop in while sitting in neutral

    Just a guess; momentary lapse of fuel pressure.
    How much fuel was in your tank? Take a look inside the tank next time it starts to happen and see if anything looks weird in there.

  6. #6

    Re: RPM drop in while sitting in neutral

    Quote Originally Posted by Trials View Post
    Just a guess; momentary lapse of fuel pressure.
    How much fuel was in your tank? Take a look inside the tank next time it starts to happen and see if anything looks weird in there.
    Heat has caused me issues with tank pressure before

  7. #7

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    Re: RPM drop in while sitting in neutral

    I wouldn't increase your idle, why bother as the bike isn't stalling when the rpm drops.

    As it is going to be brutally hot today and tomorrow why not go for a spin and see if it happens again. In addition to other advice I'd check your tank vent (cap ??) and any vacuum lines in the fuel delivery system.

    Also, aside from what the PO says re this not happening before has the exhaust been changed and/or maybe the stock ECM settings as well.
    PS

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  8. #8

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    Re: RPM drop in while sitting in neutral

    So I took her out for a but today running some errands (damn was it ever hot). The RPMs at idle were a bit rough until the bike reached 90 degrees or so. After that it was idling nice and smooth like usual. I'll keep an eye out for it, but I'm not too concerned atm.
    Not too sure what would have caused it to idle rough like that for only a short period of time.

  9. #9
    Robbo's Avatar
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    Re: RPM drop in while sitting in neutral

    Maybe bad gas ??? Happened to me too but not since I stopped eating burritos .

    Seriously though, bikes donít like the really hot weather. All of mine are air-cooled. I donít even think about riding in heat like this.

    If itís not something that happens consistently under somewhat normal operating conditions, I wouldnít worry about it too much.

    Btw, staying in gear at red lights is much safer in case you need to quickly move away from danger.

    Stay cool and ride safe


    Sent from my iPhone using Tapatalk

  10. #10

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    Re: RPM drop in while sitting in neutral

    Another update. Bike was running very poor today. Headlights started flickering, then turned off. When I was on Hwy my throttle stopped working, popped the clutch and it started going again. When I pulled in my garage the. Cluster light started flickering, the RPMs were stuttering and then it stalled. Turned it back on and the headlight was back on. Correct me if I'm wrong, but these signs are pointing me towards a bad/weak stator?

  11. #11

    Re: RPM drop in while sitting in neutral

    Quote Originally Posted by arogal View Post
    Another update. Bike was running very poor today. Headlights started flickering, then turned off. When I was on Hwy my throttle stopped working, popped the clutch and it started going again. When I pulled in my garage the. Cluster light started flickering, the RPMs were stuttering and then it stalled. Turned it back on and the headlight was back on. Correct me if I'm wrong, but these signs are pointing me towards a bad/weak stator?
    Do the usual multimeter test at the battery terminals. It could be the regulator/rectifier, battery on its way out OR the rotor/stator.

  12. #12
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    Re: RPM drop in while sitting in neutral

    Before doing ANYthing else, check that both battery terminals are securely connected.

  13. #13

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    Re: RPM drop in while sitting in neutral

    My first guess would be a bad harness connection OR an intermittent positive or ground problem. Since the problem seems to be moving around, I might check the main connectors in your wiring harness for oxidation (may look slightly pink or green), then the main power and ground connections. Be sure to look at the contacts in your main fuse too. When I unplug any wiring on a bike, I use contact spray and a light coating of dielectric grease to clean and protect connections.

    A bad stator can cause problems in some cases, but on your bike the ignition and FI is powered off the battery -- since it cranks enough to start, there should be lotsa power for those systems. I'd bet the charging system is not your issue -- it's something else.
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  14. #14

    Re: RPM drop in while sitting in neutral

    I had this problem on one of my kawasakis just the other day. Mine was a faulty old battery.

  15. #15

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    Re: RPM drop in while sitting in neutral

    Popped the seat off yesterday evening and the negative connection on the battery was SUPER LOOSE. This should explain why it was only hapenning here and there because once it lost a solid connection over bumps/vibration on Hwy.
    Tightened it up and just got back from a ride. Nothing unusual anymore. Feel like bikes vibrating at 8-12k rpm, but I think I'm just over thinking things now.
    Time for an oil change, it's been 4000km
    Last edited by arogal; 07-03-2018 at 08:02 PM.

  16. #16
    Riceburner's Avatar
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    Re: RPM drop in while sitting in neutral

    That would explain it. Good it was a simple fix. Had my batt short once and shut off the motor, with a metal kickstand plate that bounced around under the seat to land crossing the terminals.

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