Surging Idle

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Surging Idle

This is a discussion on Surging Idle within the Z1K/Z750 Maintenance forums, part of the Kawasaki Z1000, Ninja 1000, Z800, Z750 & Z-750S category; Hi all, my 06 Z750S has had a kinda strange issue the entire time I've owned it. It has your typical 'surging idle' issue, but ...

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Thread: Surging Idle

  1. #1
    Newbie jtbask11's Avatar
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    Surging Idle

    Hi all, my 06 Z750S has had a kinda strange issue the entire time I've owned it. It has your typical 'surging idle' issue, but only under very specific conditions - when the bike is fully warmed up, turned off for any amount of time, then turned back on while still at operating temperature. The surging idle isn't too bad (maybe +-100 RPM) but makes the bike sound like crap. It basically goes wubwubwub and sounds like it has a very aggressive cam in it. The engine does not come close to stalling and otherwise operates normally. The problem goes away after getting up to driving RPM for any amount of time, or by pulling the choke slightly. Idle at any other point, hot or cold, is near perfect.

    I changed the spark plugs today (pretty sure it was running the originals with 14k miles) and while it made the engine a little more responsive did nothing for the surge. The bike has a Two Brothers slip on and a PC5 with the appropriate mapping. The old plugs were dark, HOWEVER the last time I ran the bike was cold with the choke pulled for about a minute or two so I think this is not an accurate reading of the operating conditions. The bike did not reach operating temperature.

    Searching online shows that idle surging is typically an issue for carb'ed bikes that are running lean - however this bike is FI and has the proper map so it should not be lean. Furthermore the very specific conditions of the surge have me puzzled. I was advised to just ignore it, the bike runs perfect all other times but the perfectionist in me wants to fix it.

    Has anyone ran into an issue like this? I can try and post a video tomorrow.
    2006 Black Z750s - Two Bros Slip-on - PCV - 2010 ZX6R Shock - Tail Tidy Kit - LED Taillight with Integrated Turn Signals - LED Rear Turn Signal Strips - Puig Frame Sliders - Corbin Gunfighter Seat - Denali Sound Bomb Mini 115db Horn - SpeedoHealer - Chinese Universal Mirrors with Integrated Turn Signals - Black Bolt Kit - Driven D3 Grips - Black Shorty Levers - LED Gear Indicator - Crappy Nylon Water Bottle Holder

  2. #2
    Up-And Comer saganb85's Avatar
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    Does the pcv have the warm up mode unabled? It will add fuel for a certain amount of time anytime the bike is cranked doesn't matter if it's warm or cold unless it has a temp sensor also. Mine does it with zx10 throttle bodies but I have it enabled since there's no manual choke

  3. #3
    Newbie jtbask11's Avatar
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    It does not have it enabled, I typically use the manual choke on a cold start. The bike will run without it, but idles a little low around 900rpm.
    2006 Black Z750s - Two Bros Slip-on - PCV - 2010 ZX6R Shock - Tail Tidy Kit - LED Taillight with Integrated Turn Signals - LED Rear Turn Signal Strips - Puig Frame Sliders - Corbin Gunfighter Seat - Denali Sound Bomb Mini 115db Horn - SpeedoHealer - Chinese Universal Mirrors with Integrated Turn Signals - Black Bolt Kit - Driven D3 Grips - Black Shorty Levers - LED Gear Indicator - Crappy Nylon Water Bottle Holder

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  5. #4
    Up-And Comer saganb85's Avatar
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    Bump the idle up to 1100 then hook to a laptop and try pulling a couple points off the fuel table at idle and see if it changes anything. Don't be scared to play around with the mapping too much the downloadable maps aren't perfect and really need fine tuning the afr maps they used were way off in my opinion

  6. #5
    Newbie jtbask11's Avatar
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    When warmed up it idles right around 1200. I'll try messing with the idle screw to get it closer to 1100 and adjust the fuel mapping from there.

    The PCV maps do kinda suck tbh. They add in tons of gas (up to like 38% more at midrange RPM and moderate throttle application - where I spend 90% of my highway riding). It does make for some sweet flames when I let off after being hard on the throttle

    I've been considering getting a pro dyno tune after doing valve clearances.
    2006 Black Z750s - Two Bros Slip-on - PCV - 2010 ZX6R Shock - Tail Tidy Kit - LED Taillight with Integrated Turn Signals - LED Rear Turn Signal Strips - Puig Frame Sliders - Corbin Gunfighter Seat - Denali Sound Bomb Mini 115db Horn - SpeedoHealer - Chinese Universal Mirrors with Integrated Turn Signals - Black Bolt Kit - Driven D3 Grips - Black Shorty Levers - LED Gear Indicator - Crappy Nylon Water Bottle Holder

  7. #6
    Up-And Comer saganb85's Avatar
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    You should definitely try a different map or get autotune and get a more correct map for your setup really in the long run it's better than a dyno

  8. #7
    Newbie jtbask11's Avatar
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    Essentially the only tunes for the z750 I saw on the Dynojet site was for either stock or Two Bros slip on - which is what I have and am currently running.

    Out of curiosity, why would an autotune kit be better? Wouldn't a pro tuner be able to make better adjustments?

    And a little off-topic, the tune I'm running gives trash fuel mileage. Cruisng 80-85 mph on the highway I get like 33 mpg.
    2006 Black Z750s - Two Bros Slip-on - PCV - 2010 ZX6R Shock - Tail Tidy Kit - LED Taillight with Integrated Turn Signals - LED Rear Turn Signal Strips - Puig Frame Sliders - Corbin Gunfighter Seat - Denali Sound Bomb Mini 115db Horn - SpeedoHealer - Chinese Universal Mirrors with Integrated Turn Signals - Black Bolt Kit - Driven D3 Grips - Black Shorty Levers - LED Gear Indicator - Crappy Nylon Water Bottle Holder

  9. #8
    Up-And Comer saganb85's Avatar
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    What model are you looking up? When I was running stock displacement there were about 30 maps for the z750s. Autotune will always adjust to the environment and elevation changes or any modification added to the bike down the road can also add a switch to have a mpg map and hp map. If you're running stock gears you should be getting at least 40 mpg with a good map. I'm getting 35 with 7 teeth up and 950cc

  10. #9
    Newbie jtbask11's Avatar
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    I was looking at 2006 Z750. There are a bunch of other maps but they're all euro models - the US model has 3 options, stock z750, stock z750s, and two Bros.

    I looked into the auto tune, it seems a pretty involved process. A lot of people had issues unless they blocked their PAIR valve, made individual maps per gear, linked the coolant temperature, and some other stuff I can't remember. Do you run an auto tune? If so where did you mount the bung? I would assume that best place would be in the headers right after all four pipes combine.
    2006 Black Z750s - Two Bros Slip-on - PCV - 2010 ZX6R Shock - Tail Tidy Kit - LED Taillight with Integrated Turn Signals - LED Rear Turn Signal Strips - Puig Frame Sliders - Corbin Gunfighter Seat - Denali Sound Bomb Mini 115db Horn - SpeedoHealer - Chinese Universal Mirrors with Integrated Turn Signals - Black Bolt Kit - Driven D3 Grips - Black Shorty Levers - LED Gear Indicator - Crappy Nylon Water Bottle Holder

  11. #10
    Up-And Comer saganb85's Avatar
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    The pair valve is simply a little silicone can take care of that. The bung is right after the 4 pipes turn into 1 tilted up as high as possible. No need for all the other stuff. I'd recommend just trying the euro maps then pick the one that is best but the Autotune would get you where you need to be within a couple hundred miles of riding. Supposedly not supposed to let it tune below 1500rpm but changing the o2 parameter made it possible for me.

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