bike surging???
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Thread: bike surging???

  1. #1

    bike surging???

    Since i got my bike (92 zx7) this summer, it seems like the bike is surging till after 5,000rpm.... it starts jerking when you try to hold a constant throttle.. When reving it with the clutch in, it is fine, so i'm kinda confused now..... any ideas???

    Thanks in advance

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  3. #2
    this is my...boomstick! Array CrotchetyRocket's Avatar
    Join Date
    Aug 2002
    click, click
    Lots, but, first, when was the last time the thing had new plugs? Do that. The adjust your chain tension to spec.

    If no help, then fiddle around with the idle mixture screws. You'll have to remove the tamper plugs, if they haven't been but on a bike this old that is likely handled already. Check to see they are set to approx. factory settings and equal. Then, try a 1/2 turn in and a 1/2 turn out from those settings to see if any help is afforded. E back your results then.


  4. #3
    Moderator Array TeeTee's Avatar
    Join Date
    Feb 2002
    Out to pasture in the 'Wack
    04 Kawi Z1000,
    Start with the simple stuff like the plugs and chain as suggested. But assuming the previous owner put in a jet kit it sounds to me like you're slightly rich. I've been playing with my carbs for more than a year now trying to dial in the tuning with my butt dyno and have run into a lot of what you are describing.

    First off the surging usually comes from being too rich in that speed range. Not enough to seriously foul the plugs but enough to set up a lurching when trying to run at steady speed. From what I've learned at 3000 to 5000 the problem is more likely with the vacumn piston needle heights. If your surging at cruise problem is present from 1500 to 3500 as well then the idle pilots also need to be leaned as CR suggested. Assuming you've had a jet kit put in that bike try lowering the needles by 0.5mm via clip change and adjustment shims and see if that helps. Then try some 3500rpm roll ons. You need to do this quick but with control and see what happens before it climbs above the 5K mark to test that area of the tuning. It should pull clean and hard as you roll it open. If it helps then try a further 0.5mm at a time until it runs clean at the 3000 to 5000 range. When it pulls hard for the first part of the roll on and then sags during the later part of the roll up to WFO then you've gone too far and it needs to be richened again.

    For the lower end just close the idle pilots until you can putter along cleanly at steady throttle but it still idles smooth and pulls away from stops with a barely cracked throttle cleanly with good torque and no dropout bogging. Up to a point the engine will idle better with a richer setting and rough with a lean setting. I tend to close the screws until I notice a slight rpm drop then upen them up one step and find that works pretty well.

    And as always if all this is like Egyptian Heiroglyphics to read then take your bike to a mechanic that has some decent tuning senses and have them play with it. Setting this stuff up takes a good 3 to 6 trips into the carbs at about an hour a pop so be prepared to be patient and do it yourself or pay some money to get it set up right.
    A backyard mechanic without a service manual is just like a hooker without a lamp pole.... they are both in the dark.

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