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no spark on mini dirt bike - gay

This is a discussion on no spark on mini dirt bike - gay within the Chinese/Import Minis - General Discussion forums, part of the General Talk category; allright, i was rodding the fuck out of this little chinese knockoff dirt bike thing that i got from my friend for 50 bucks, and ...

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  1. #1
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    apexrift's Avatar

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    no spark on mini dirt bike - gay

    allright, i was rodding the fuck out of this little chinese knockoff dirt bike thing that i got from my friend for 50 bucks, and it pulled wheelies and shit and it was tight as hell, but then i crashed that bitch HARD maxed out in 4th. it rode for about 10 miles after that, then the chain came off, because the crash loosened the back end and pulled the rear tire forward, and when the chain broke, it slapped the magneto deal inside the transmission. when you take the casing off the left side of the tranny, you see the sprocket the chain goes on, a little magneto deal on the bottom right, some wires coming out of the top, and a flywheel-like thing that turns when you crank the motor, and it looks like there's some timing marks on there, but you take that off, and there's 2 coils under it. one has 1 wire coming off of it that goes to the cdi box, and the other has 2 wires coming off that dont do anything (were never hooked up) and then there's the magneto, that has 1 ground wire, and one wire that goes to the cdi box. all together there are 3 wires coming ouf of the tranny. when the chain came off, it broke the transmission where it holds the magneto in place, so it would just flop around. so i got a spare motor and put it on my frame and it gets no spark, and i've replaced EVERYTHING in the wiring (i got all new wiring) but its still not getting spark. by the way, there is a magnetic bump on the flywheel thing that looks like its supposed to get REALLY CLOSE to the magnet on the magneto, probably to tell it when to spark... anybody else have this problem?



    when i got the wiring i got a new coil, plug, cdi box, and replaced the coil and the magneto in the tranny. what else could be wrong? ARGHHH and why does only one coil hook up? whats up with the bottom one that has 2 wires on it that dont do shit? and how does the other coil even work with only one wire on it?


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    xr88honda's Avatar

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    hmmmmmmmm

    first thing i would do is unplug the killswitch to rule that out then triple check my wiring just to make shure i didnt hook something up wrong then make shure the coil bracket has a good ground (aka the little green wire) but it sounds more serious then that .so if that works punk rock if not good luck

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    five0addict's Avatar

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    the 2nd coil is an extra 12v outlet, for lights or whatever. (dont just hook up a bilb ) id say your wiring is wrong.
    yea i still ride

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    could the magneto be fucked? i used a fluke meter to make sure there were no broken wires, and there are only 3 wires - how could i get them mixed up? the killswitch is unhooked, because it's a normally open switch (meaning that if you unhook it, it will run, if the wires are touching, it turns off) i took an electronics class by the way... the green has continuity from the end of both green wires to the engine (touch the end of the green wires and touch the engine with the fluke meter, it beeps, and shows 0, indicating no resistance, i.e. continuity.) the blue wire with the white stripe and the black wire with the red stripe have continuity all the way through. spark plug is new, gapped to .025, the only thing i can think of is that the magneto is fucked. where could i score a new one? i might be able to upload a picture of my wiring, but i don't know if my digicam has batteries - if not, i'll buy some and post some pictures. one of my friends was saying "aaw shit dude, if you fuck with the magneto then it fucks everything up all the time" blah blah blah but THEY DONT MAKE THESE THINGS TO GO 21 MILES AND BREAK DOWN!! they wouldn't waste their time casting the engines to only last a little bit, you know? where can you buy spare magnetos for these?









    couple more questions - what is the gap supposed to be between the magneto and the magnet on the flywheel that sticks out? is there supposed to be a gap, or are they supposed to touch? (i would think there would be a gap) right now its set at .008. also, does the coil BRACKET have to be bolted to the frame to be grounded?

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    It's not a magneto, it's a hall effect sensor. It generates a light pulse every time that bump on the flywheel goes by. That coil with one wire is the exciter coil, it's sole purpose, to provide juice to the ignition coil.



    So, flywheel spins, builds up a charge in the ignition coil



    Bump passes sensor, CDI grounds the ignition coil



    Field in coil collapses, inducing a high voltage charge in it's secondary winding, which feeds the spark plug, which happily discharges it to ground after making it hop a tiny gap.



    So, you have a few things to verify. The exciter coil, ignition coil, cdi, and sensor. Replace things ONE AT A TIME to determine which is the culprit.
    TTR --- Never Challenge an Engineer

    #77 - 05 Honda CRF70F - 6.9hp



    Sponsored by: Moto Milano - TBolt USA - AHP Minis

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    holy crap, that is the most intelligent reply ive ever gotten in a forum! well i'll go ahead and check all those things again, and tell you guys whats up. should i just replace everything again, even though i got entirely new wiring? and how would i go about testing the sensor? it doesn't show continuity between the bump on the sensor and the blue/white wire coming out of it (it probably wouldn't though, since i'm guessing the current is inducted though magnetism). is there anywhere you can buy parts for this?

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    The sensor is pretty much a replace and see if that fixes it item, unless you have an o-scope handy. : )



    You should be able to unplug the exciter coil, put a meter between it and the motor, set for voltage (not sure if it's going to be AC or DC on the exciter, one coil, DC I think) and get a reading when you kick it over.



    I'd wager the ignition coil is fine, haven't seen one of them crap out yet.



    The CDI, again it's a replace and see item.



    Go over your work again slowly, verify all connections are good and tight, your ground is solid, etc. Also make sure everything is plugged in where you expect it to be. I ended up redoing a Jackass harness by hand after discovering that under the electrical tape, some lines had been spliced three or four times, so what was blue and white at one end was red and black at the other, etc. Use the meter in continuity mode to tone it out, and if it doesn't match your expectations, redo it. Given you had spark before, I'd put your old wiring harness/cdi back on, leave the stator plate and it's contents under the flywheel of the motor alone, and see what that does.
    TTR --- Never Challenge an Engineer

    #77 - 05 Honda CRF70F - 6.9hp



    Sponsored by: Moto Milano - TBolt USA - AHP Minis

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    frdvschvy's Avatar

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    My money is on the exciter coil. These cheap chinese ignitions are prone to failure.
    2004 SDG 124cc GPX engine, I-shock, Tappet breather, Kitaco Inner Rotor kit, Oil Cooler, 24mm carb, Uni 2 stage filter, Ported intake, Yoshimura TRS pipe, One industries graphics, ASV clutch lever, Red Baron mount w Two Bros pegs, 12" wheels. Special thanks to Vince at TBolt USA!

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    exciter coil works

    well i tested the exciter coil, and it appears to be working - it shocked the fuck out of me when i used the fluke meter, and it read around 200-250 Vdc, so thats working, and when we hooked the exciter coil directly to the ignition coil (bypassing the hall effect sensor and cdi box) i got 1 volt out of it. not enough to make it spark. and when i changed out cdi boxes with my friend's, his worked fine, so it HAS to be the hall effect sensor - by the way, did i tell you that when the chain broke, it broke the transmission casing where it holds the hall effect sensor? and when that happened the HEF smashed up against the bump on the flywheel, so i did a motor swap, (which already had its own wiring and such) and now it won't spark. so i'm 95% sure the HEF went bad somehow.



    story of motor swaps.



    when i laid mine down on the concrete at 55 mph, i mutilated both my arms. this was about 6 days ago and i still have open wounds that i treat twice daily... anyways, it ran fine for about 10 more miles (give or take) and we rode it around a parking lot, then we put it in a truck and drove it to another parking lot (bigger) and it wouldn't start. we tried starting it for 2 hours. sometimes it would kind of start, but wouldn't stay running. then after about 2 hours, everytime we kicked it over it would make this RATTLE noise, then it siezed up. we took the cover off and found that the tranny casing was broken where it held the HEF and it had smashed into the flywheel bump. so i say "fuck" and do a motor swap with my friends dirt bike - which was crashed, ran fine, then never ran again after 10 more minutes of riding. all he did was drop it (the rotary gears in the tranny screwed him up, he shifted into first after 4th gear and locked the back tire up. so i take the motor off, put my finger over the spark plug hole, and ensure that it has just as much compression as the other motor. its fine, so i bolt it up, and use the existing wiring. WOAH!! no spark? hmm, so i switch to my original wiring from the first motor, and still no spark. i get NEW wiring, and no spark. his HEF didnt smash against the flywheel, it looks fine. i just need to find a place to buy a new HEF - could i just cut one off of a car with abs and rig it onto the tranny ??? eh....
    poo

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