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Louie
Louie, Technician
Category: Motorcycle
Satisfied Customers: 11453
Experience:  25+ yrs. experience
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Have 2009 muv700 big red that won't start. I have replaced

Customer Question

Have 2009 muv700 big red that won't start . I have replaced stator with ckp sensor because of erratic readings, also coil due to bad primary reading. It will turn over and back fire every now and then . The fire is red so checked pcm on another machine and ran fine. When watching fire at plug it starts out strong then gets weak. I've checked and cleaned grounds and also applied extra battery for proper voltage while cranking to no avail. Could you please help?
Submitted: 5 months ago.
Category: Motorcycle
Expert:  Louie replied 5 months ago.

Hi Gary and welcome to JustAnswer,

Thank you for the question and your patience. Should you still need assistance for information purposes only...

Initially , re-check the 30A and the 2 X 10A fuses as well as the ignition switch (even if just to completely eliminate them as potential suspects).

Still and on the described symptom of "...fire at plug it starts out strong then gets weak...", proposed preliminary checks (if have not been done and depending on the version & wiring) when attempting to start:

  • • presence & consistency of IGN+12V on the black/yellow wires from the main relay to the PCM and the ignition coil;
  • • presence & consistency of IGN+12V on the black/green wire from the FI 10A fuse to the PCM;
  • • very low pulsating voltage between the blue/yellow & the green/white wires of the CKP sensor to the PCM;
  • • pulsating voltage on the green/orange wire from the PCM to the ignition coil;
  • • verify PCM's green wire is tied to a good chassis and engine ground as well as to the battery's - terminal.
Customer: replied 5 months ago.
Checked everything you said again . Still has red fire and won't start back fires every now and then
Expert:  Louie replied 5 months ago.

Consider an experiment; i.e. disconnect the blue/yellow & the green/white wires from the CKP sensor. Momentarily / repeatedly touch these freed wires to the terminals of a 1.5 AAA battery. This is to simulate a pulsating low voltage.

There should be spark (ignition ON):

  • if no, then back to wiring, connections, PCM, ignition coil checks;
  • if yes, then a CKP sensor issue or how the sensor is triggered.