I have two 1986 Yamaha Moto4 225 ATVs one runs fine the other has no spark.  I have changed all parts including the stator assy and still no spark.  I changed the parts from the one that does not spark to the one that runs and it runs.  I have taken all the readings, voltage and Ohms, reference in the maintenance manual and they read the same on both machines except for the coil output which is 0 on the one that does not spark.  I have ohmed out the harness with all plugs unplugged and no shorts were detected.  Any advice or suggestion would be greatly appreciated.  

do you know any thing about how the starter gear works on that model?I have an 87 225 that the starter gear won't disengage on  

I too have an 86' Moto4 225. I can't get spark either. How do you know if there is a short in the stator assy. I unplugged the connectors and set my ohm meter to (Rx100) and placed (+)lead on one of the white wires and the
(-)lead on the other alternating between all three. I have 0 for readings. Is that good or bad?
I have a manuel but it's not clear..... SOS  

confused Bob  

check all of the connectors if you haven't already,  it is possible to get a good continuity reading on the wires but not get a good connection at the connectors when you plug them together.  

Have same issue ... could it be the CDI box?
What else have you guys found out about it?
PLease Please email me
zamaro@comcast.net

Richard