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will 2008 yfz450 run with battery disconnected


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i have gone through two brand new battery in two rides it starts and runs great then with no warning it just dies. the battery wont charge after. it shorts out and I have to replace it. my question is should the bike run with the battery disconnected. I have a new battery in now and changed the rectifier and when I take the cable loose it dies. is this normal

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Hey @go2glamis welcome to Quadcrazy. I would check your stator coil.   It could be over charging the system. Or not charging at all.   You need to see what voltage you have coming from the stator as well as do an ohms test on it.   The engine should run with the battery disconnected, the lights and accessories would not work properly and may shut the engine down if you were to turn them on due to a heavy draw but the engine should run with the battery disconnected. 


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Here a few pages from the manual. It’s not the same year but should be close enough if not the same.  

I would also start the bike up and put a tester on the battery and see how much voltage your getting at the battery.   As your checking rev the engine a little and see if it changes. Are you handy with an electrical tester ? 





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  • 2 weeks later...
  • 2 weeks later...

OK new stator is in i can disconnect battery now and the engine still runs so definitely the stator was bad. now i was hoping that would solve my other problems to but didn't.  i don't ride at night much but my headlights don't work and i can only start the bike with the clutch pulled in (wasn't this way new) the tail and brake light work. is there a fuse or relay for these? i changed the neutral sensor before but didn't help 

i can rebuild or troubleshoot almost any engine but am horrible at electrical     

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As far as the starting the bike with the clutch pulled in thats normal. Most likely solved that with the neutral sensor.  You may have never knew it but that’s how it works.   As far as head lights that can be traced back to the power source.  Either a bad connection or fuse.  Pull the connections at the lights and test for voltage. There should be three wires on your headlight.  One is a ground two others are high and low beam.  Start there and check for power with the head light switch on obviously. 

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