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Weak battery affect spark?

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So here's the deal. I bought a non-running '02 DRZ400E from a guy that gave up on it and left it outside for a few years. It's in pretty rough shape, but I got it for dirt cheap. So I finally tracked the issue to a torn up stator because the starter clutch bolts had back out. I bought a used stator from a guy here on TT and installed it last weekend. Now the plug fires when I first crank the motor, but then stops and still isn't consistent. The battery is weak, and don't really want to buy a new one until I know this bike is going to run. Kind of a newbie question, but can a weak batter cause no spark? Appreciate any help...

Also, I looked under the FAQ for a thread that I once saw on testing electrical system, but no luck. Anybody know where it is?

Thanks

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Did you try and bump (jump only if the other battery is removed from the vehicle) start it? When the bike is trying to start wit the button, voltages can drop very low. If they drop much under 12.5V, then yes, a too weak battery will make it impossible to start.

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I haven't tried to bump or pull start it due to 5" of fresh snow snow. I'll need to wait a few days until snow clears. I haven't jumped it yet either. I have a few street bike batteries that I could pull out and use to jump.....not a bad idea.

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The CDI needs 12 volts DC more or less to fire. That can come from a battery or the alternator. (normally you have both) I'm not sure at what voltage the CDI will stop firing but I'm sure it is well below 12 volts. People with non-functioning alternators report the battery will run the ignition until the LCD display dies on an S bike.

Your best bet right now is the jumper the bike to a good 12 volt battery and see if it will run. You may still have alternator/stator problems. No good way to bench test a used unit and they have a history of failing.

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I was in a similar situation a few weeks ago. even when jumping off from a charger the non-runner i just bought it would not stay running once the starter button was released. I used jumper cables to a truck battery I had at the shop and it fired right up. If it's been siting for years there is a good chance the carb is gummed up from the old gas so you may have to disassemble and clean it if you haven't already.

edit: mine had a very weak spark if any at all just to clarify.

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