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  1. #1
    Pwgsx's Avatar
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    760 Voltage Issue

    I am trying to track down why this ski keeps running like crap and backfiring. I got a tester on the battery and found the voltage will drop from 12v to 3v to 9v, back to 12 while running. Here is a video of it idling and giving it a little throttle. If I rev it up more it sputters really bad and backfires. What could this be? Its a new battery.


  2. #2
    Probably a bad engine ground. But could be faulty regulator.

  3. #3
    Pwgsx's Avatar
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    Ground is good, tried testing the reg. but not sure what I am looking for. Ordered a new one so we will see.

  4. #4
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    On the older Yamahas I usually suspect the lighting coil, obviously it's not used for lighting on a ski BUT it is used for supplying voltage to the CDI.

  5. #5
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    Ok I got the new rectifier in and it tested correctly. I installed it last night and at idle volts were constant and climbing to 13v. So I know that is working and the charging coil is good. When I press the gas it is still backfiring and bogging. I pulled the plugs and the front plug is very wet and the back plug is black. Now I know the black and the tons of smoke is from the added oil bc this is a new engine from sbt. Here is a video of it backfiring and bogging. If I rev it higher it might rev up and then BOOM, it will backfire very loud. What should I look at next? It seems to me the front plug is getting a weak spark or random spark or none at all. I tested the coil and only got .1 on the front side and nothing on the back. Anyone have a shop manual that they can send me??

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  6. #6
    Myself's Avatar
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    I'm betting stator is shot. Test AC output voltage while cranking on the lighting coil.

  7. #7
    Pwgsx's Avatar
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    Well I tested the stator and it was good. Tested the ignition coil and the one side was good but the plug wire side was dead. Ordered a new coil and it runs perfect now. Need to water test but no backfiring.

  8. #8
    the coil fires both plugs simultaneously it is known as a "Wasted spark" ignition. More than likely it was just the plug wire not the coil itself..

  9. #9
    Pwgsx's Avatar
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    I split the plug wires with a razor and it was in pretty bad shape. Had more than 1 break and the other didnt look so hot either.

  10. #10
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    I've seen that also. I put new leads on one last year that was burnt about every 2" internally.

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