Just started to misfire one day

Discussion in 'Electrical' started by dcstrawn92, Dec 19, 2014.

  1. dcstrawn92

    dcstrawn92 New Member

    Okay here my situation. i was riding my bike one day on a 10 mile journey to my school. I was about 7 of the 10 miles when i thought my bike was starting to run out of gas. I knew i had just put gas in the day before so i was thinking there was a leak that drained the gas out. Checked the gas tank to see that it was still about 3/4 full of fuel. So i limped my bike home so i could see what was the matter. I thought it was a fuel mixture problem. I broke the bike in with a 16:1 oil gas mixture and has since reduced it to a 20:1 I emptied all of the fuel and tank and completely washed it out with water to make sure there were no particles in the tank. I cleaned both of the fuel filters and there were no particles in them. I ended up taking the carborator completely appart to see if anything was clogging the jets and nothing was in there. I adjusted the c-clip just to make sure the right amout of gas was getting into the engine which had no affect on the problem. I looked at the electrical system to see if there was any problem with that. There was little to no spark coming for the spark plug. I replaced the spark plug with an ngk plug and put it to the gap of .025. It started to work okay for about the first mile and then began to misfire again. The next step i took was to replace the CDI box which greatly reduced the misfiring for about ten miles, but then the problem came back up again. There is now no spark created by the spark plug. Im not sure if this could be a problem with the magneto. Could you please help me out.
     

  2. butre

    butre Well-Known Member

    is it magneto or is the bike just overheating?
     
  3. crassius

    crassius Well-Known Member

    mag is easy to test with a meter - could just be a bad ground

    20:1 seems high, so you may be clogging the muffler

    also check that engine mounts aren't loose making carb shake too much
     
  4. dcstrawn92

    dcstrawn92 New Member

    The bike isn't overheating at all because it doesn't run long enough to over heat. How do you test the magneto?
     
  5. dcstrawn92

    dcstrawn92 New Member

    What setting should the tester be on? And what readings should I get. If 20:1 is too high what should the fuel mixture be? I just tightened up the engine mounts yesterday and the problem is still there.
     
  6. crassius

    crassius Well-Known Member

    I like 32:1 and the goal is not to make the mounts tight, but to be sure the motor is tight - one should not be able to push or pull the motor sideways while holding the bike frame

    set your meter on ohms and look for either 350ohm or 480 ohm (plus or minus about 20%) from the blue wire to a ground bolt at the head - if bad, then test around inside mag cover for a bad ground
     
  7. dcstrawn92

    dcstrawn92 New Member

    okay i don't think it was the oil gas mixture just because im not even getting a spark right now. the motor is tight so i don't think that's the problem. for the ohms test it tested inside the parameters but still doesn't create a spark. i replace the spark plug but it still doesn't spark. any other suggestions.
     
  8. crassius

    crassius Well-Known Member

    may be a bad CDI, but you should look closely at your spark plug cap to see if it is broken inside
     
  9. dcstrawn92

    dcstrawn92 New Member

    i tested both of my cdi's and it seems like both of them have gone dead. Is it possible that my original and a replacement went dead after not much use.
     
  10. crassius

    crassius Well-Known Member

    last month. I had 2 new ones go bad within an hour or so - 3 weeks ago another new one died - this is not common though and I suspect that the new 480ohm mags may be a problem with some of the CDI units - all the ones that went bad were the newer rubber-boot type
     
  11. dcstrawn92

    dcstrawn92 New Member

    would you suggest upgrading to a rocket racing cdi or an hd lighning cdi or stick with buying the stock cdi's from china
     
  12. butre

    butre Well-Known Member

    Get a Jaguar or an HD Lightning, the rocket racing CDIs aren't that great.
     
  13. crassius

    crassius Well-Known Member

    I use the stock CDIs, but some folks like the expensive type. I've never tried one, so can't say if there is any difference.
     
  14. KCvale

    KCvale Motorized Bicycle Vendor

    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.
    Note:
    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 my repair is done.
     
  15. dcstrawn92

    dcstrawn92 New Member

    why would you say that the rocket racing isnt that great. do you know the differences between the jagurar and the lightning that set them appart from each other.
     
  16. dcstrawn92

    dcstrawn92 New Member

    to kcvale

    the magneto is good. i just tested that all out and its testing perfectly. i just ran a current through my cdi with a trickel charger and tried to get a spark and didnt get anything. so im only guessing, but i think the problem lies within cdi
     
  17. butre

    butre Well-Known Member

    the rocket racing cdi uses cheap parts
    the hd lightning has a more aggressive timing curve than the jag does
     
  18. KCvale

    KCvale Motorized Bicycle Vendor

    Of course you didn't get a spark from a DC trickle charger, the CDI needs an AC pulse to fire.

    Are you sure you followed all those steps?
    If your CDI ohms out to the plug cap you either have a crap plug or a weak mag magnet.
     
  19. dcstrawn92

    dcstrawn92 New Member

    to brute

    do you have an hd lightning or a jaguar

    to kcvale

    well i hooked it up to a tester and i could never get a good reading it would always jump around even if we weren't doing anything to it.
     
  20. butre

    butre Well-Known Member

    I use an HD Lightning, but the Jaguar is better if reliability is a bigger concern than raw horsepower.
     
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