Please help .....bayou 300

[Jason Compton]

Hi all,, I have a bayou 300 and my problem is it only fires when I turn the key on ,the motor is not being turned over,,,turn key off,,then turn key on and it sparks, ,,,?,,, I installed new stator,pickup coil,cdi ,and rectifier, ,,,any help would be very appreciated. ......

Edited February 14, 2018 by Jason Compton

[Frank Angerano]

Hey Jason, welcome to Quadcrazy. So I’m assuming by the way you explained this, is that you have the spark plug out of the engine and you turn the key on and off and back on and you see a spark at the plug? What started all the parts/replacement work ? Can you give a little background with the bike was it a running bike? Something happen out of the blue ? And the year of the bike? 

[Jason Compton]

It was bought not running,,I was told the cdi was bad..I installed a new one with no luck...so I threw a new stator,pick up coil, ,and rectifier, ,,still no spark while turning the engine over only when I turn the key on and off...I installed a gm module and it fired up ...only I can rev it due to no timing advance in that module...I am lost ...

[davefrombc]

There  may  be  a  wire crossed .  If  you  get spark  turning the  key on and off but no  other time ,  it  seems to  me  there  is  a constant  voltage  going either to the  circuit in the  CDI box that triggers  a spark  pulse or directly to the  spark  coil.  Spark  coils  work  by  the primary  fields in it  being   charged by  a  current  and then  discharging through the  secondary  to  send  a  high voltage   shot to the spark  plug..   If  you have  an  old   car spark  coil you  can see what  I mean  by  connecting  it  to  a battery.  No spark  is produced  by  it  until  you  disconnect  the  power to  it ..  Then  you  get an  instant spark.  It  is the breaking  of the  current to the  coil that triggers  the  spark.

[Frank Angerano]

Gm module ??

I would go back to basics for a minute.  Was the new cdi an oem or aftermarket ? I’ve put two aftermarket cdi boxes on bikes that did not work. An oem box worked so I’m leary about aftermarket cdi’s if that’s what you used. 

 Was the stator installed correctly ? And pick up coil? And the gap between the pickup coil and stator? Should be a non adjustable and only go in one way but double check. 

I would also get a tester and take an ohms reading on the new stator and pick up just to be safe that they are working and within the range as per the manual. As far as the regulator goes I’ve used aftermarket and they have worked for me but nothing like oem parts! 

This is going to sound stupid but it worked for me and a few other people I know to determine if my cdi was bad. I baked it in my oven for 10 min @  250 deg  and let it cool off and put it in and I had spark.  Most cdi boxes go bad because of moisture inside.  Warming it does in fact get the moisture out and will work for a while but not a permanent fix. I would put the orignal rectifier back and try that with the old cdi if it’s not an original (oem) part you used.

Aside from that you should take the tester and go through wiring and relays starting from the battery up to the controls and looking at the neutral safety switch, look for any broken or hit wires along the frame. What year is the bike ? 

[Frank Angerano]

@davefrombc has a good point. Someone could have tapped a wire thinking it’s a 12v for some accessory and it’s backfeeding.  Look for anything out of the norm that does not belong to the original wire  harness.  Good point Dave.