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Louie
Louie, Technician
Category: Motorcycle
Satisfied Customers: 11418
Experience:  25+ yrs. experience
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Pickup: 1994 yamaha warrior 350 with a weak spark i..coil

Resolved Question:

1994 yamaha warrior 350 with a weak spark i changed the pickup coil and it did not help
Submitted: 7 years ago.
Category: Motorcycle
Expert:  Louie replied 7 years ago.
Hi, welcome to JustAnswer and thank you for asking me this question,

Almost always, a weak spark is either:
  • battery is weak or ignition +12 is low or exciter voltage is low;
  • not cranking fast enough.

Initially, try:
  • remove the sparkplug, crank & do a spark test with the plug attach to the HT wire and laid to the engine;
  • with a voltmeter check if the ignition +12 would go below 10.5.

Bear with me as I could not be more specific, for some reason, I could not locate the wiring diagram nor the service manual for the Yamaha YFM350X. It's just here somewhere in the hard disk. Will keep on looking. This is just to let you know that I got the notice on your problem.

Good luck and thank you for using JustAnswer.
Customer: replied 7 years ago.
remove the spark plug, crank & do a spark test with the plug attach to the HT wire and laid to the engine. i did that i get a i spark very light almost pink in coler i tryed to us a spark plug tester to jump the spark and i get nothing
Expert:  Louie replied 7 years ago.
Hi again, I checked your other post and it would seem that you replied but it was closed.

"check the coil's resistance; terminal to ground (primary) should be very low something like 0.1 ~ 0.3 ohms well i did this and it came up as 0.00 what dose that mean" if the primary of the ignition coil reads 0 ohms, then it is shorted
and would require replacement. This would resut to weak or no spark at all.

Other checks:
  • pulsating very high ACV on the orange wire when cranking (from CDI to ignition coil);
  • pulsating high ACV between the red & white / green wire (from the exciter) when cranking;
  • pulsating low ACV (~0.5VAC) between the blue & yellow wire when cranking;
  • black / white wire from ignition switch and black / yellow from engnine kill switch must not read 0 ohms to ground when switched ON;
  • IGN + 12 on the brown wire from the ignition switch to CDI.

Postback results of tests.

:
Louie and other Motorcycle Specialists are ready to help you
Customer: replied 7 years ago.
i changed the ignition coil and that did not work now what should i try
Expert:  Louie replied 7 years ago.
Postback results of the tests on:
  • pulsating very high ACV on the orange wire when cranking (from CDI to ignition coil);
  • pulsating high ACV between the red & white / green wire (from the exciter) when cranking;
  • pulsating low ACV (~0.5VAC) between the blue & yellow wire when cranking;
  • black / white wire from ignition switch and black / yellow from engine kill switch must not read 0 ohms to ground when switched ON;
  • IGN + 12 on the brown wire from the ignition switch to CDI.
Customer: replied 7 years ago.
it was the cdi box
Expert:  Louie replied 7 years ago.
Thanks for sharing the info.

Ride safe.