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Hunting/Surging idle Z750

Discussion in 'Maintenance and Servicing' started by NothingExpert, Sep 11, 2013.

  1. Hey guys,

    I've been doing some research but not making any headway into this issue. My Zed is hunting at idle. It also tends to be a bit boggy off the line (but I think this is natural). The surge/hunt happens regardless of engine temperature and becomes a bit more pronounced at higher temperatures and as the fuel level get lower. Power delivery once off the line appears to be fine.

    The only mod the bike has is a K&N Filter.

    I'm yet to test coil packs but will be on the weekend.

    Other problems I thought/researched and might be related are:

    Throttle body balance
    Fuel filter/pump issues

    People have told me the hunting is due to running lean. As I do not have a PCIII I'm not sure how I can adjust my A/F Ratio to test this apart from muck with the mix screws on the throttle bodies?

    Any suggestions welcomed...

  2. #2 mike8863, Sep 11, 2013
    Last edited: Sep 11, 2013
    According to specs I found a 2004 Z750 is fuel injected.
    The only way to adjust the fuel mixture is a PC or similar device. Fuel volume and delivery is controlled by the ECU.

    The screw on the throttle bodies ( pt 16014 in the diagram below ) is described as " screw - pilot air". If it operates as you would expect then screwing it in would reduce the amount of air introduced to the circuit ie. more fuel less air. If I was to adjust this screw,first thing I would carefully screw it all the way in counting the number of turns so that I could reset it to its original position should it not have the desired effect.

    z750throttle bodies.

    Simple test...put the standard air filter back in....does the problem go away?
  3. touch of injector cleaner in the fuel is worth a try
  4. Thanks for the replies. I've had a bottle of cleaner through it. Unfortunately I don't have the original filter as I bought it with the K&N.
  5. Does it have a vacuum motor or electric stepper motor to control the idle speed or is it a stop screw only? Maybe the idle control is playing up if it's a vacuum or stepper motor.
  6. Unfortunately its not that fancy. It's just a stop screw. I checked the coils on the weekend, did some leak investigation and found nothing. Pulled out the fuel pump assembly only to find that I couldn't get to the filter (nearly destroying the pump mounting screws in the process.

    Came to the conclusion that it could be an injector that is not delivering enough fuel.

    The surge happens up until approx 3500-4000rpm but the bike doesn't lose power at the wheel. It just sounds like it is spitting seeds out. After 4k it runs like normal.

    I think I might take it to a kawaka dealership for a service and ask them about it.