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Testing a Yamaha 650/701/760 electrical system

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  • Testing a Yamaha 650/701/760 electrical system

    This was not written by me - but there seems to be enough people here that have electrical issues that it may provide useful to post it. The information below was specifically written about 61X and 62T motors, but applies to any Yamaha waverunner with a 650/701/760 motor since they all have basically the same components.


    Well, the season is here. Since so many have electrical ignition questions, I thought it would be handy to keep this "quick test" guide at the top. I hope this helps everyone make a quick diagnosis 8)

    This applies for most any ignition problem with the 701 61X or 62T series ignition components.

    1. check the AC output of the "charge" coil. Don't get confused with the term "charge" coil......this is what Yamaha calls it, as it "charges" the cdi capacitor. This coil can generate in excess of 500 volts!!
    Dis- connect the brown / white trace wire and ground wire and connect the meter leads to these wires, and while cranking the engine, observe the reading. You should have 30 to 50 volts AC depending on how good a battery and starter you have.

    2. Check the pulser coil output. It's job is to tell the cdi when to fire the energy stored in the capacitor. Dis- connect the white / red trace wire and connect the meter leads to this wire and the ground wire. You should get a pulsating 4 to 5 volts AC. (ps, an analog meter is best for this test)

    3. If you are having problems with the battery not recharging, then dis- connect the two green wires and read the cranking voltage produced by the "lighting" coil. This coil's name is a throw back from the old enduro bike days, when the manufacturer would add a coil to the stator to operate head, brake and turn signal lights....without a battery, and later with. Anyway, you should see 6 to 10 volts or so here, again AC. This coil puts out close to 20+ volts AC, to be recitified to DC and regulated at 13.5 or so to recharge the battery. This coil is rated to generate up to about 2amps of charging current. This in mind, beware when running two bilge pumps.....a battery going bad (high internal resistance) and two bilge pumps running for a extending time is just enough to cook a lighting coil.

    4. Ignition coil. Not many folks do not have a meter capable of resolving the almost dead short of the primary on this coil. But if you do, the resistance should be .078 to .106 DON'T forget to subtract the meter leads resistance by shorting together and subtracting, or adjusting the zero ohms pot, if you have it. Also, remove and insert the leads in the sockets to clean the connection.....I often see 1 ohm or more go down to .2 or .3 by performing this task.
    NEXT, check the health of your spark plug wires, or high tension wires as the Brits like to say. The only way to test them properly is to remove the boots and get to the end of the wire. You can try jamming the point of the meter probes into the end, but due to the dirt and metal dust, it often does NOT give a solid connection / reading. If you have electrical contact cleaner, by all means spray with that first. You should read 3500 to 4700 ohms, or 3.5 to 4.7K ohms STEADY....while flexing the wires from end to end. If you get any fluctuations, they are bad...IE breaking up inside, turning to a high resistance powder of metal and rubber. I have seen bad plug wires cause problems with idle and low speed only, mid range only, and high speed only, and every combination thereof. Very strange !!!

    If all these check out good, then I would swap the cdi with a known good unit....and known good means just what it says.....you have had it running in your boat, you removed it, and you put it away..The only other known good is a new unit. I have heard many a sad tale of days of trouble shooting with no luck, only to find out that the "known good" cdi your buddy gave or loaned you was not good after all.

    Another interesting point is the "sparks when you let off the start button" syndrome. This always means on of two things......the cdi is bad, or the pulser coil is bad, or the wire from it to the e box is open.

    Another good point to keep in mind: it is very possible to have two problems going on at once. One, like bad plug wires may have going on for a while, but no creating any major problems....the performance degrades so slowly you really don't notice it. Then, the charge coil insulation starts breaking down, or the connection from the winding to the terminal posts goes bad and starts arcing over. The two combined creat havoc, and can make diagnosis difficult.

    After seeing so many stator coils have a good resistance, but test bad....I strongly advise against using resistance readings alone a gauge of health. Perform the cranking voltage output test!! Resistance readings are still useful for some work, so here they are for 61X and 62T:

    61X: charge coil, brown / white trace to ground / black: 365 +- 10%

    Pulser coil, white / red trace to ground / black: 12.6 to 15.4

    62T: Charge coil, brown / white trace to ground / black: 497 to 608

    Pulser coil, same as above

    Lighting coil, green / green wires: 1.14 to 1.40 Since this coil is not grounded in any way to the stator frame, you can check this coil for leakage to ground (indicating bad insulation) by measuring between either green wire and ground with your meter set on the highest ohms scale, usually 20 to 40 meg ohms. If you get any reading, the coil is going bad.

    There are other tests we perform to positively verify a coil's health, but the equipment is specialized and the proceedure is beyond the scope of this posting.

    A note about the ignition coil: CDI ignition coils are much different than the coils in many cars, especially older cars. Those coils operate on the "collapsing magnetic field" principle to creat the high voltage. CDI ignition coils are in essence "step up transformers" simular to any any plug in wall transformer to operate various devices. The output is directly proportional to the input.

    Another interesting proceedure you can do to gain more information about your coil's health.......hook your meter up to any coil, set it on the highest scale, and observe the reading. Leaving it there for an hour or more and come back and see what it reads. A lower reading or higher reading, or a reading that will not stabilize indicates a bad, or going bad coil. This may only work with better quality meters.

    Some of this applies to Kawasaki too. If you want more info on Kawasaki, as well as Polaris, please contact John at Jet Ski Solutions

    EDIT: Thanks for the very useful info, Penguin, but no thanks for the spam.
    Last edited by JB; August 23rd, 2010, 06:50 PM. Reason: soliciting business

  • #2
    Re: Testing a Yamaha 650/701/760 electrical system

    Thanks for the good information.

    I have a 1999 Waverunner GP760 with no spark. I went through the tests and everything looks good except for the pulsar coil test. The coil tests OK with an ohmmeter. I only have a digital meter (Fluke 77), so I wasn't sure I would get the voltage reading stated. I do have an oscilloscope, so I tried to hook that up and look for short pulses. I did see very short little pulses, so I figured the pulser coil was OK. The pulses I saw may have been noise.

    Thinking I had eliminated everything else, I purchsed a brand new CDI from a Yamaha dealer. With the new CDI, I still have no spark.

    Has anyone tried testing a pulsar coil with a digital meter? If so, what voltage did you see? If I am not getting trigger pulses, what is the likely cause? I'm thinking the coil or a connection. Is there a magnet on the flywheel that passes by the pulsar coil to create the pulse. Could it be the magnet or flywheel? That sounds like somewhat of a pain to check and/or replace.
    Last edited by 89SeaRay160; June 22nd, 2012, 06:17 PM. Reason: Correction
    -- 1989 SeaRay 160, Mercruiser 3.0L 135 HP --

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    • #3
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      Re: Testing a Yamaha 650/701/760 electrical system

      ya i just tested the pulser coil. i got 4.6 volts ac. its quite easy. and yes there are magnets all around the inside of the flywheel. should be the smallest coil pack on your stator. the white with red stripe wire and ground of course. if your geting no voltage than it cant trigger the cdi to let out its charge.

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