need Tune Up help on the GP420 motor

Discussion in 'General Questions' started by Torques, Mar 8, 2008.

  1. Torques

    Torques Guest

    Can anyone help me with the tune on the GP420 motor? I have read on the internet the tuning instructions regarding this motor. When I first ran the motor, cruising at 20 mph, it was firing as smooth as silk. Then after around 5 miles, it started to bog out. I adjusted the high screw clockwise which fixed the acceleration bogging problem. But what I notice is this: when cruising at 20, it makes that dieseling sound, not the clear whine sound. When I am accelerating, the firing is smooth as silk but when I stop the acceleration to cruise speed, the dieseling sound returns, kind of a uh sound instead of the whee sound. I don't want to hurt the motor. Thanks in advance for any ideas.
     

  2. kawasaki999

    kawasaki999 Member

    turn the low needle in till it stops 4 stroking.
     
  3. Torques

    Torques Guest

    Low needle, not the high? The only reference I have read about the low needle is for idle problems.
     
    Last edited by a moderator: Mar 8, 2008
  4. kawasaki999

    kawasaki999 Member

    low is 4 low speed turn it in. if it does not work turn it back. both needles have an affect on each other, so you might have to richen up the high once you lean the low. Just turn the low 1/4 turn in and go 20 mph and see the difference. your idle will probably will go up meaning u was rich on the low.
     
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