Help with intermittent spark - 78 KZ400

  • Stockton350
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Help with intermittent spark - 78 KZ400

19 Jul 2018 19:30 - 19 Jul 2018 19:30
#787241
When I check for spark (spark plug in the boot, plug against the engine case) I sometimes get spark and sometimes don't. Battery is full, boots and plugs are new, checked point gaps, new coil checks within specs. I also made sure the ground battery terminal had a good connection to the frame. Any suggestions?
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Last edit: 19 Jul 2018 19:30 by Stockton350.

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  • One1
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Re: Help with intermittent spark - 78 KZ400

19 Jul 2018 20:07
#787242
Run a separate ground to the engine block. As the mounts age and become rusted from the inside out it's possible to loose contact between the frame and block.
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  • 650ed
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Re: Help with intermittent spark - 78 KZ400

19 Jul 2018 20:21
#787244
Stockton350 wrote: ................ I also made sure the ground battery terminal had a good connection to the frame......

Frame?  I'm not familiar with the KZ400 setup, but the KZ650 ground cable attaches to the engine.  Ed
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Re: Help with intermittent spark - 78 KZ400

19 Jul 2018 22:07 - 19 Jul 2018 22:08
#787248
650ed wrote:
Stockton350 wrote: ................ I also made sure the ground battery terminal had a good connection to the frame......

Frame?  I'm not familiar with the KZ400 setup, but the KZ650 ground cable attaches to the engine.  Ed

400/440 attaches to the frame right beside the battery. cable is 4 inches long.
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Last edit: 19 Jul 2018 22:08 by One1.

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  • VTEC
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Re: Help with intermittent spark - 78 KZ400

21 Jul 2018 16:10
#787356
Check the voltage drop on the power feed to the coils. There's an accumulation of lost voltage there including the ignition switch, kill switch, and all the old connectors in between. 

Next time you have no spark check the voltage at the coils compared to the battery. The difference is voltage drop. You may even have nothing due to an intermittent open in the circuit.
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  • Fischer779
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Re: Help with intermittent spark - 78 KZ400

21 Jul 2018 19:21
#787368
Did you check the Plug Gap? Spark plug gap may be different on new plugs. Might want to check that and remove a variable. 
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