Engine Trouble motor appearing to run out of fuel

Discussion in '2-Stroke Engines' started by matti, Jun 17, 2012.

  1. matti

    matti New Member

    Been having a problem with what I thought was the motor at times running out of fuel which is not the case as i have checked & doubled checked by opening up the vent screw & observing the flow. I checked the spark plug & installed a new one with same results. Finally I removed the spark plug & observed a very weak spark as I engaged the motor while peddling. I am leaning towards a faulty coil. any suggestions would be appreciated

  2. Fabian

    Fabian Well-Known Member

    Do yourself a favour and get a new magneto (just to be sure) and get yourself a Jaguar CDI kit to replace the original CDI.
    On a stock standard low compression engine, i've found setting the Jaguar CDI to the most advance jumper position works best; also making sure your carburettor jetting is correct.

    If you haven't done so already, and have a spark plug location that's pointing straight up, get an NGK BP6HS.
    If you have a slant cylinder head, get yourself an NGK B6HS sparkplug
  3. KCvale

    KCvale Motorized Bicycle Vendor

    It really helps to spell out exactly what 'The Motor' is whenever you ask a question, there are a bunch and they differ.

    I recommend that if you have a Skyhawk motor straight or slant head get yourself an NGK BPR6HIX Iridium plug. http://SickBikeParts.com has them for $8 and worth twice that, it is a performance boost you actually feel.
    Note, the 6 is a temperature range.
    The higher the number the more the plug dissipates heat.
    It's summer in the dessert so I stock 7's here to dump as much heat as possibe, 6's are good all temp plugs, 5's are for really cold climates when you want to keep your motor warmed up.

    CAUTION! The Iridium plugs can be too long for the cheaper motors!

    Here is another tip, the 24G wiring in all these kits are junk from the motor mag to the CDI, especially those banana connectors.
    I pop the mag cover and cut all 3 wires off the mag and run a round black 18G power cord type wire like a PC or your drill uses for a power cord soldered from the trimmed down CDI wires to the ground and top lug of the Mag on every build I do.
    I leave the white wire snipped off at the mag lug since you can put your kill button across the two CDI wires to kill the motor too.

    I actually take it farther on all my builds with my own black wire the size of a bike cable from the kill button to the CDI and epoxy on a spiffy box over the connections but that's not the important part.
    The important part is to get every milivolt the mag puts out to the CDI and a good plug to spark the fuel mix.

    With no pictures or even what motor make and type there is no telling, but if your gas line is next to your head that will cause your problem when the motor heats up and running wide open. The gas gets hots and you get a vapor lock in the gas line.

    I hope that helps and good luck with it.
    Last edited: Jun 17, 2012
  4. jaguar

    jaguar Well-Known Member

    the gas cap isn't breathing and you're getting vacuum lock which is relieved when you take the cap off.
    drill a teeny tiny hole in the cap.
  5. matti

    matti New Member

    The motor is a sky hawk 66cc slant head & the gas line is not next to the head. I will consider making the wiring changes Thanks for your input
  6. matti

    matti New Member

    I checked the gas cap & it does breath but I will drill a larger hole in it & serif that resolves the issue Thanks for your input
  7. matti

    matti New Member

    Thanks fabian for your input where is a good firm to purchase these items
  8. motorpsycho

    motorpsycho Active Member

    it's possible that your float level is set too low, which will make the float bowl run out of fuel.
    the flow of fuel from the gas tank is not fast enough to re-fill the bowl before the float drops all the way down.
    even tho the needle & seat is open to allow fuel to flow into the bowl, the engine is using the fuel faster than it can be re-filled in the bowl.
  9. matti

    matti New Member

    I will try to adjust the float & see if that makes a difference
  10. KCvale

    KCvale Motorized Bicycle Vendor

    Adjusting the float is tricky.
    There is a little tab between the 2 float arms that aligns with the needle that regulates the gas flow in the middle.
    If you want a higher fuel level tweak the tab towards the float bowl cross bar just a LITTLE.
    If you get fuel in the overflow move it away.

    NOTE Beware the float bowl pin! It likes to fall out with the float bowl off.