Coil voltage week spark

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Gingerweeman
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Coil voltage week spark

Post by Gingerweeman » Sun Mar 17, 2019 11:47 am

Ok I need help before I torch this bike. Bought a bandit 400 non runner. I won’t go through all the things I’ve checked the list is long. One thing I’ve noticed is I have only got 12v to the right hand coil when the ignition is on. 0 volts to the left coil. When cranking the left coil gets intermittent voltage only seems to be around 3-5 volts. Also getting a week spark from the left coil plugs 1 and 4 but strong spark from 2 and 3.
So should I be getting 12v to both coils with the ignition on?

SevenThreeSeven
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Re: Coil voltage week spark

Post by SevenThreeSeven » Mon Mar 18, 2019 3:45 am

Yes, you should be getting 12v power supplied at both coils. Whenever one coil gets power the other should be getting it too. Both coils are supplied power by the same wire.

The power supply to the coils is a very simple bit of wiring. You should start at the right-hand coil (the one that alway gets 12 volt power when you key-switch to "on") and trace that line backwards. You shouldn't have to go far before finding the splice for the other coil 12 volt wire (the coil power supply wires are colored Orange on every wiring schematic for every model of the bike). This same wire leads back to the fuse box and also to the ignition switch.

Unfortunately, buying a "non-runner" means you really need to be good at electrical system trouble-shooting. The starting point in dealing with a non-runner would be to trace the bike's wiring harness to insure that things are proper and OEM. Best to find out right from the start whether a prior owner has done some sort of horrifying hack-job on the wiring.


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