Question about 2004 Yamaha YZ 450 F

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YZ 450 STARTING PROBLEM

I have just installed a new uprated stator coil on my yz 450 2004 to run lights on my bike as well as the spark plug. However it wont start now at all? I have spark and when i kick her over i do get smoke from the exhaust? every now and again she will back fire like a rifle shot going off. Ive checked all the connections and emptied the carb bowl and flushed the carb through. i keep getting a spark but does the spark need to be a certain strength? It seems normal and strong, and ive also put in a new spark plug? someone please help? Is it the timing or is there some kind of internal shut off for lack of oil or coolant, i just dont know,

regards chris penny

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  • Anonymous Jan 31, 2009

    i HAVE a yamaha yz450 quad that will not start I cheanged the plug and set the gap just keeps turning over not even a cough from it

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Hi and welcome to FixYa,

Offhand, the backfire is significant. It indicates that fuel is getting inside the combustion chamber and it further confirms that there is spark. Being the case, it would appear that this is now a timing issue. A couple of ideas to explore:

  • compare the original stator coil and the uprated one; are the coil location on the same side, on the same angle, on the same distance from the edge;
  • there would be a guide notch on the base plate of the coils, are they identical and does it fit exactly back into position;
  • there would be a guide/lock pin that keeps the magneto/flywheel in position;
  • there would be timing marks on the magnet/flywheel that must coincide with marks on the engine case.
Good luck and Thank you for using FixYa. Happy Holidays.

Posted on Dec 15, 2008

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