Hello, and a bizarre issue

Discussion in 'Introduce Yourself' started by Suds, Jan 11, 2015.

  1. Suds

    Suds New Member

    Hi everyone. I'm glad to be a part of the forum. I've been messing with gas scooters for about 10 years, and just decided to build one of these.

    Interesting issue. I built the kit, fired it up and it idled for about 30 seconds nicely. Then it died. Fired it up once more, it jumped from me for a second, so I physically stopped it. Hasn't started up since. ( I figured to be as detailed as possibly with the lead up)

    It's an electrical problem for sure. I assumed it was the magneto getting wet somehow so got a new one. Nothing. I'm now waiting for an NGK plug and boot, but from my experience, I doubt a plug could fail just like that (unless it could/does?) While I'm waiting, has anyone had their new engine's electrical fail so quickly without any clear signs?

    Wired correctly, no kill switch, getting fuel, good compression.

    Thank you!
    Last edited: Jan 11, 2015

  2. KCvale

    KCvale Motorized Bicycle Vendor

    This may help...

    My troubleshooting procedure is simple these days.

    Disconnect everything.

    Ohm the black magneto wire to a head bolt, it should read a dead short.
    If not, check the ground tab on the magneto.
    The new skyhawk CDI's have no white wire, ground is the lower connector but it has a wire from it to ground.

    Old style mags with a white wire have a tab out of the mag that solders directly to the mag base and they can come loose, just hold it down and re-solder.

    Ohm the magneto from the black and blue wire, 320-380 ohms is ideal, an open or dead short means a bad magneto if the wires are connected.

    Ohm the CDI in the 10K-20K scale.
    Red+ meter probe to CDI black wire.
    Black- meter probe to the spark plug cap.
    You should get about 6.9K ohms.

    If not it could be a bad wire or cap.
    Unscrew the plug wire at the cdi, use pliers or even cut it off and dig the junk out if need be and do the same test above again to the cable screw on the CDI.
    If that works get a new wire and plug cap, if not you have a bad CDI.

    If all of that is good there is only one thing left, the magnet.

    That was indeed the problem with this repair on a new build with a 2014 gasbike.net front page engine kit.

    When you pull the 4 bolts out of the magneto mount it should slam itself against the magnet, I mean to the point where it is hard to even get your first bolt in.
    A weak magnet that lets you move the mag around pretty easily is not strong enough to create a spark which is what this repair had.

    Magnet replaced, problem solved and that repair is done.
  3. bluegoatwoods

    bluegoatwoods Well-Known Member

    Nice magneto/CDI troubleshoot guide, KC.

    To the OP: Can you edit the title of this thread to something like "Magneto troubleshoot"?

    Then it'd be searchable for future users.
  4. jaguar

    jaguar Well-Known Member

    remove the shellac from the stator coil frame where the four screw heads press against it. That is the ground path for the ignition system. the shellac can prevent good electrical conduction there.
  5. KCvale

    KCvale Motorized Bicycle Vendor

    Regardless of where, the coil ground needs to be a perfect dead short ground to the spark plug base in the head.

    Without that you will never get a spark, the plug needs a - to the magneto - so we use the engine metal.
    Like any 'wire' it can have a poor electrical connection via gaskets and other insulating things, hence why you test the Magneto (black -) ground wire to the CDI to the head to make sure it is dead short like a wire because it actually acts as one.