CDI is Toast. Payday is FRIDAY. Anyone have any dirty hacks?

Discussion in '2-Stroke Engines' started by Wisski, Aug 24, 2010.

  1. Wisski

    Wisski New Member

    So I'm very sad. I had just gotten the entire peddle assembly replaced on my Frankenbike, and accidentally jimmied the sparkplug boot. Took it off to re-seat it, and the guts of the boot just fell right out (actually, pushed out by the spring inside). This disappointed me, as I have no replacement, but I figured I'd just slide the wire (which has a copper core) over the spark plug tip (which was a perfect fit). I thought it was working fine, as the bike started right up, but it appears that the CDI didn't much like this, because about two miles down the road I lost all power. I tried a couple hill-assisted starts, and amazingly, i managed to get spark, but only above 25mph. Found out the hard way that engine RPMs had to stay high, otherwise, no fire, engine stall, and Mo' Peddling. I'm guessing heat conducted into the CDI through the wire, and destroyed something, I can't imagine what.

    So now I have a Mo' Peddle, and a CDI that the multimeter confirms is shot. I still have a week worth of work to go to, and an 8 mile bike ride to get there. Anyone have any dirty hacks for getting spark? I have no SCRs, and the only HV transformers I can get my hands on are the kind that sit on the circuit boards inside CRT and LCD monitors. I'm handy putting circuits together, but maybe not so much on designing them. Also, I'm lazy as heck and don't like peddling 16 miles a day. PLEASE HELP! :(

  2. G-Superior

    G-Superior Member

    Never seen that happening because of that but you can try to take it apart and rewind it all up with new (second hand from something else like a transformer but it has to be the same diameter and lenght!)
    Poople used to do that a while ago with old engines and some still do, so you can give it a try plus the cheap copper that the chinese use is probably no good compared to copper from a high quality transformer
    All you have to do is:
    Get rid of all the plastic that there is around it to seal it and remove the wire put some new one in and then seal it up again with electrical tape! Easy!
    Godd luck
  3. adb140275

    adb140275 Member

    bake it in the oven at 350 degrees for 25 minutes, and allow it to cool completely off before trying to use it again. this normally doesnt work, but my friend got it to work once. good luck
  4. Wisski

    Wisski New Member

    :-/ I was under the impression the entire box was filled with epoxy...Excuse me, I have to go cut open my CDI now! :grin5:
  5. Al.Fisherman

    Al.Fisherman Active Member

    Something else must of happened. There is no way that a wire hooked from the CDI directly to the plug would cause the CDI to burn up. It has to be something else like a CDI ready to go. Every engine that the spark plug wire is made with actual wire in it connects from the CDI to the spark plug itself. The wire in the CDI or plug might of been having interment contact, and that caused the CDI to die. You could use bare wire from the CDI to the plug and run the will be a shock hazard but will run.
    Last edited: Aug 24, 2010
  6. G-Superior

    G-Superior Member

    tells us how it goes! If people used to do it and it worked you should be able to get it back to life! Hehee
  7. Wisski

    Wisski New Member

    Al - It was just a guess (I'm not a mechanic type, but trying to become one). I found the REAL problem when the new CDI came in...

    The ground connection on the magneto coil is totally buggered. Intermittently it will be conducting, and that's what threw me, cause when I tested resistance on the coil, it was about where it should be instead of wide open. I tested it again after the new CDI came in, and NO GROUND. grrr. Some creative use of solid core wire and solder has solved the problem, somewhat. I can't take it above 25, otherwise vibration and/or heat compromises the connection, but it'll run now...with either of the 2 CDI units I've got -.-;

    So new magneto coil is on the way. *sigh* I HATE trying to troubleshoot a system that has a sporadic-contact issue I'm unaware of. WAAARGH! :mad:
  8. GearNut

    GearNut Active Member

    The ground connection is notorious for being what is called "cold soldered" from the factory. The worker melts solder onto the connection until it looks good.
    This type of solder connection has poor adhesion between the parts and a higher resistance through it.
    A proper solder connection is made when the connector and wire are both heated to the point where the solder will melt when touched to both of them, soldering iron removed first.
    The wire and connector parts will have a very good bond to the solder and a lower resistance will be had throughout the connection.
    It will also be darned near vibration proof.
  9. Al.Fisherman

    Al.Fisherman Active Member

    Out of all the engines I've bought ALL had a crimped terminal, secured under the coil mounting screw, for their ground connection. As far as the White wire, I cut it at the coil. The blue and black wires are removed and replaced with a single non spliced higher grade wires to the CDI, which is under my gas tank. I do this before gas is ever put into the tank.
  10. machiasmort

    machiasmort Active Member

    Gearnut describes a process called tinning. What you do is heat up and coat both joinging contacts with solder sepperately.

    You then proceed to heat them both together (to join them) so a good electrical bond is obtained!
  11. HeadSmess

    HeadSmess Well-Known Member

    ok, ive had a fair few motorbike style cdi units fry on me from not using a proper boot with resistor. these are the types with a charge coil and a seperate trigger coil, and a few more wires...4 or 5.

    its to do with back emf caused by the spark, that upsets something.


    ive rarely seen a simple 2stroke cdi thats required/used an insulated boot...

    i thought i had this exact problem myself as my boot had recently collapsed.

    upon investigation...these things have me scratching my head really hard...

    i believe the HT motors are what i would call a zbox... with three wire systems. black, blue, white.

    originally, as instructed, it was black/black, blue/blue(the only two to the cdi/coil) and white/killswitch.

    one day, it suddenly stopped, a mile from home. nothing down the first hill... second hill i tried PRESSING the started! wtf? killswitch is still fine, btw. not suddenly reversed its operation.

    so earthed the white wire. which has been fine, albeit a slightly weakened spark, until my boot fell apart.

    this time it was a 20 km ride back home, with me pushing boot down onto plug! i tried just sticking the wire onto the plug, and hey! it got worse, until... i pedalled the least 2km :( (dont throw old boots over your shoulder)

    got home, changed boots, and its been running yes, but not very nicely, until my newly ordered cdi arrived.

    slightly improved, but white still needs earthing...and i said SLIGHTLY improved

    leaving me with the sneaking feeling its actually the pickup coil on the flywheel thats the problem.

    ive resoldered those wires and got 34 ohm across the coil, and 2M+ to earth at either end...normal? iunno. ordering a new one of them too, now...

    but, I DO NOT GET HOW THESE CDI UNITS WORK! especially if the white wire was not connected to earth in the first place... unless there is an internal connection to ground (tap)in the pickup winding. which my multimeter says there isnt.

    if there was, i get them. if there wasnt.... wtf?

    the failure of such a connection does explain why my white wire now NEEDS to be earthed...

    look at it this way. blue comes from the pickup coil. provides charging power for the cdi. black is earth. where does the other end of the pickup coil go to complete a circuit? apparently, the white wire. but thats the kill switch when earthed! so, therefore, there must be an internal tap.

    THEN the system starts to resemble a chainsaw unit, that has been cut in half, and has the other half in that little black box...


    iunno. all i wanna do now is make a new flywheel, then machine the case to mount a chainsaw cdi unit, with the added benefit of a heavier flywheel :) then i can adjust the timing ;)
    Last edited: Sep 4, 2010
  12. GearNut

    GearNut Active Member

    HeadSmess, Here's a schematic. I hope it helps you out.

    Attached Files:

  13. Wisski

    Wisski New Member

    Gearnut - It's not the joint that's the problem (Since problems started, I've solder-sucked that joint out anyways, and re-soldered). From laminate frame to the point where the coil's ground exit the plastic holder, it's a totally solid, 0 Ohm connection. BLUE->Ground is around 35 M Ohms (Big Problem). BLUE->WHITE is about 350 (These turns are OK!). The ground wire itself is probably broken off somewhere inside the coil, where I can't get to it to repair.

    Which isn't surprising to me - it looks like the electrical sadist errrr...worker, used a 4000 watt soldering iron to make the joint. Burned the insulation off the wires, at least down to the casing (I'm not inclined to unwrap the windings just to see wtf this idiot did). I don't know if it was just the current pull across unrated wiring, or the "worker" and his mini arc welder, but my ground wires CRUMBLED at the joint when I tried to re-solder. I had to carefully solder them to a rated wire, and then solder THAT to the laminate.

    Al - At least on mine, that's just a solid connection point. There's a separate wire coming out of the white plastic case that holds the windings, and is soldered to the laminate, grounding it, and the entire engine case.

    HeadsMess -

    I'd say not. When my coils ground connection is acting up, it's around 340 ohms BLUE->WHITE, and anywhere from 19-35 M Ohms between BLUE->Ground and WHITE->Ground, indicating that there's a poor, or non-existent connection to ground.

    There is a connection to ground - There should be a few tiny wires coming out of the top/bottom/side of your generator coil, connecting to the steel laminate (It may be on the OTHER side of your coil!). The solder joint connecting your coil to ground is probably failing like mine was. GET IT SOLDERED SOLIDLY BACK ON NOW - otherwise you run the risk of the wires stressing INSIDE the coil, and mine has.

    Yup. Blue is about 90% of your windings, and white is tapped somewhere around the 10% mark. White is NOT a kill wire. It is an accessory power line, so you can run lighting/electrical (lol, in theory). Your kill switch should be replaced with a waterproof toggle switch (or a keyed ignition switch!), and spliced into the blue wire, and placed somewhere easily accessible while riding!

    I'll have to try doing this on purpose on my bike...My ground is utterly demolished, so its either peddle till I can get a new coil, or turn white into ground. Thanks for sharing this - I probably wouldn't have thought of this on my own! :grin5:

    *gets the soldering iron heating up!*
  14. Wisski

    Wisski New Member

    OK! Soldered WHITE->Ground. Took her around the neighborhood (I LOVE mine - 2 high grade hills, and about a 1/2 mile of straightaway). Peppy acceleration, good power (20-ish mph WOT) on a 20 degree and 30 degree hill, and almost 30mph on the half mile. Sounds like she's hitting every stroke. No bogging at WOT. This is a VAST improvement over the failing ground connection. I LOVE IT! XD

    Many thanks to you Heads, for sharing your problem. Helped me fix mine till I can get a new coil! :D
  15. HeadSmess

    HeadSmess Well-Known Member

    thanks gearnut :) 2 seconds of looking at that and there it is! the elusive ground tap :) right there on the magneto, as i suspected.

    clears everything up. :D

    and no probs, wisski :) sorta only found it out by accident anyway...why would anyone try using the killswitch to start something? :lol:

    and and and, this means i can actually have a rectifier etc and run a few fancy LED spotties? phwoar! :D
    Last edited: Sep 5, 2010
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