Kill switch a killer?

Discussion in 'Electrical' started by Rockin_Roll, Sep 11, 2015.

  1. Rockin_Roll

    Rockin_Roll New Member

    The four months I've been riding my 2-stoke Skyhaw bike has been, as the Craig list's seller said it would be, a complete blast! I have not a bit of worry or moment of regret -- well not exactly, but that's nothing to do with the bike, and for another post. But this is for something that is indeed cause for worry and concern. Two, three months into the almost daily riding, maybe 5 to 10 miles a day at most, the kill switch went dead. Just wouldn't work anymore. I'd press the button, only after coasting to an almost dead stop, but the engine would still be purring pretty as ever. I'd gently release the clutch and she would halt, pretty as you please.

    Couple of weeks ago I'd riding along and the engine/motor just stops. Bike keeps going with the momentum, the engine stops as if somebody pulled the plug. And it wouldn't start, after twenty or so attempts. I noticed the coil leading from the CDI seemed a bit frazzled so I ordered a souped-up CDI from bikeberry, along with a new 3-point plug (I know there's a bit of a row about this, but I have other types as well}. Took the bike out today and she still won't turn over. I hear and feel the poppin' compression, but no, just like before she won't turn.

    I notice on You Tube some jokers with otherwise good working bikes are often stalled on starting because of the kill switch. Tho it's never made clear just how that keeps an otherwise good bike for turning over. Just how does that happen? Could that be at the root of my problem? If so, how did the bike continue to perform even after the switch was a goner. I'd like to order another one, but I sure would like to know if there something else I should look at which might be at fault before having to spend another week waiting for something which may not be the cause at all, get me? Appreciate any insight from you good folks.

  2. HeadSmess

    HeadSmess Well-Known Member

    kill switch is useless, get rid of it...

    if you use it to short the cdi wires... you get a low voltage but a heavy current, fuses the coils wires.

    if you use it to open circuit the cdi wires... you get a high voltage low current through the coil...flyback effects etc cause a super high voltage that destroys the insulation between the wires in the coil...

    and if you have the type that runs a white wire, and thats hooked to the kill switch... certain death of magneto incipient!

    its not that hard to pull in the clutch, stop with the brakes and just stall the engine out by dumping the clutch... far more reliable.

    you can fit a decent killswitch to a jag or home made cdi that works in a different area and bypasses all these troubles...
  3. butterbean

    butterbean Well-Known Member

    As to what your actual problem is now, I think the coil itself is fried. Not the black box, the coil under the engine cover. Get a multimeter and google how to test for continuity, then test the coil under the engine cover. That will tell you for sure.
    Rockin_Roll likes this.
  4. Rockin_Roll

    Rockin_Roll New Member

    Hats off to ya'll both. Wealth of info in all that, enuff for me to at least began to see some daylight. Get back here soons I have something to tell. Again, my thanks.
  5. Rockin_Roll

    Rockin_Roll New Member

    Butterbean, finally got the multimeter, checked utube for how to use the darn thing, but must confess I'm unsure just what I'm supposed to be testing. You mention the coil under the engine cover. Is this one of the wires protruding from the magneto? And further, if in fact the coil you speak of is kaput, just what will I be replacing? The coil? The engine? Sorry but as I say, I'm a complete Kramer when it comes to anything mechanical. Appreciate it if you could be just a bit more concise, and, goes without saying, your help and patience is invaluable. My deep thanks, my friend.
  6. Purple Haze

    Purple Haze Active Member

    When you get a new magneto (you will) get the newer type that only has 2 wires on it. The older ones had 3 wires, and were of lower quality. Wire a simple toggle or rocker switch into the blue wire (I fabbed a box onto the CDI to hold it) This kills the power to the ignition without shorting it out, making the whole thing much more reliable. When changing the mag, make sure it's sealed up good (RTV silicone) moisture will short out the coil.
    mikedabomb and Rockin_Roll like this.
  7. Rockin_Roll

    Rockin_Roll New Member

    Thanks, PH. Do I take it (not to put words in anyone's mouth) that is what is meant by the above suggestions of the coil being possibly burned out, the wire from the magneto? (I'll order it right away and be sure to order the newer type as you suggest.) Not trying to second guess anyone here, just trying to understand what I'm doing and why. Thanks for your time.
  8. Purple Haze

    Purple Haze Active Member

    The mag is pretty delicate on these engines, vibration used to kill them. The older ones with 3 wires were made pretty sloppy, the new ones are much more reliable and vibration proof. Leave the tie strap on the coil, then make sure the air gap around the magnet is even. There are many older threads on this forum about them to read up on if you don't understand their function. Another weak point on these is the plug wire. They screw into the CDI box. Replace the stock wire with a good quality automotive wire (I use Accel spiral core) and use a good spark plug (NGK B6HS) These mods will greatly improve both reliability and performance.
    Rockin_Roll likes this.
  9. KCvale

    KCvale Motorized Bicycle Vendor

    This is pretty easy once you know how it works and how to test parts.

    A kill button is just a momentary switch.

    Push it and it makes a connection between 2 wires, in this case the blue output and black ground magneto coil output wires under engine cover.

    In short, no voltage from the winding the magnets spin inside makes it out so, no spark, the engine dies.

    Virtually every magneto ignition system uses the 'output shorting' way to kills the engine and won't hurt anything.

    It is passive, if the switch breaks it simply can't make the connection and you ride on.

    Coil leading from the CDI?
    Pictures of your wiring would sure be nice as shotty wiring is pretty common with kits like this.

    The magneto is a coil inside the engine cover that has a magnet in that spins with engine RPM inside it and makes a low voltage in the coil with the blue (hot) and black (ground) wires as output.

    The CDI (Capacitor Discharge Ignition) module has timing circuits and big step up transformer coil to make a big momentary spark with one wire to the top of the spark plug.

    The other connection for the spark plug is the engine itself as a ground which goes all the way back to magneto coil whose black wire ground is attached to engine case.

    Any break or shot in that full circle circuit will prevent spark.

    My troubleshooting procedure is simple these days.

    Set that Bikeberry junk aside and start with what you had.

    Disconnect all the connections.

    Ohm the black magneto (in the case) 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.

    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 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 was done.

    Once you know you have spark it's fuel or compression, and in your case probably a case full of unburt fuel, ride it around with the plug out and clutch out so you can blow the junk out.

    Hope that helps.
    mikedabomb and Rockin_Roll like this.
  10. Rockin_Roll

    Rockin_Roll New Member

    You better believe it does. Was holding off on answering while juggling what to do re: ordering the magneto (decided to hold off), but couldn't hold off thanking both Haze, and KC. For the first time since I've been riding, I feel like I have a half a** understanding what I'm sittin' on. Can't tell you how much this has added to the whole experience. Now I understand the pull for serious bikers/riders and race buffs--something that goes a bit beyond the kinetic sensation of moving through the wind. I bought one of those cheap analog multi-meter at first, but then went back and got what I shouldn't got from the git-go, digital. I got rid of the old cdi when I got the new one, so am unable to pix the frazzled connect I mentioned (a serious tinkerer throws away nothin' -- I'm learning). Soons I get the time and space to follow KC's instruction, I'll report in. Again, thanx so much.
  11. KCvale

    KCvale Motorized Bicycle Vendor

    I am happy to help when I can bud, I started really documenting things about 70 builds ago and being a 30 year electronic engineer for decades the electronics are not that hard with the right meter and understanding of what does what.

    I didn't bring up timing which can be another issue like a fluke weak magnet.
    That spinning magnet has to be aligned right to excite the coil at the right time.
    I short, it at 1 O'clock on the shaft at TDC and that keyway can slip a degree or too.
  12. HeadSmess

    HeadSmess Well-Known Member

    pretty easy to put them in backwards which wont do much for performance either...

    and there was one case of the magnet itself being of reverse polarity?

    the sheer beauty of these cdi's is the simplicity.

    the magneto creates a pulsed AC waveform.
    one pulse charges the capacitor, stores it via an SCR, then triggers the SCR and discharges the capacitor at a specific point on the opposite polarity pulse, a capacitor and resistor setting this point, along with the position of the magnet in relation to the crankshaft... wha? 5 components or so? i forget...

    they also suffer from some unexpected EM effects when things like a killswitch is added...

    the only reliable way to kill them is to either prevent the cap from charging (bypass it with a resistor) or prevent it discharging (disconnecting gate on SCR)... the standard way of just shorting or open circuiting the wires fries things.... did i say it in this thread already?

    shorting the wires creates a high current low voltage in the magneto that fuses fine wires.

    breaking the wires causes a high voltage low current that breaks down thin insulation between wires.

    you need somewhere for the voltage and current, POWER, to flow...but you also need to dissipate it safely when not required! or things get hot real quick. we do this by adding resistance somewhere.

    the old "white wire" magnetos...some ran lights. some got grumpy and refused to run with lights. some refused to run unless the killswitch was held down!
    mikedabomb likes this.
  13. KCvale

    KCvale Motorized Bicycle Vendor

    hehehe, no, it's all magnet alignment.

    I suppose you could put a 1K resistor on one of the kill button wires but I just don't see it as an issue unless you do a lot of riding down hill holding the kill button in because just a second or two will kill the engine at idle, which is only producing weak power as it is.
    mikedabomb likes this.
  14. Timbone

    Timbone Active Member

    Electronics are my weakpoint. I know nothing beyond the basics. I appreciate very much these explainations and instructions. I have so many ideas...

    My solution is to keep an extra stator coil lying around just in case.
  15. Rockin_Roll

    Rockin_Roll New Member

    Good advice to check those readings before I tinkered with anything: the mag was in spec. Was damn hoping, naw praying, that was the culprit. Well, after a ton of reading on the forum here, guess I was damn fortunate the bike ran trouble-free long as it did, seeing I bought it 2nd hand from a perfect stranger: these puppies are such damn intricate mechanisms, systems within systems, all delicately balanced...when they're running, I mean. Which presently mine still ain't.

    Got that new mag, two-wire joint, was gonna hitch in on, but that'd be pretty knuckle-headed, you think, till I at least find what's holding me up in the first place, right? Well, counted out the Kswitch and since I'm getting spark, got a new CDI (NGK), and the mag and magnet seem OK, I move on to what..fuel system? The line and such?

    I see a bunch of stuff here and on tube on the working and maintenance of the carb. Is that where I go next, cleaning that sucker and what not? Again, can't say enough how grateful I am.
  16. HeadSmess

    HeadSmess Well-Known Member

    start at the beginning.

    remove plug. ensure theres spark. check.

    remove carb, stuff a drop of fuel down intake.

    try to start.

    if it starts, revs briefly, dies...its a carb or fuel delivery issue.
    if it doesnt even cough, its another issue such as the base gasket leaking, the crank seals leaking, ignition timing etc. if its used, possibility the top ends stuffed. rings and cylinder plating. remove head and have a squiz. head gasket...?

    there are only three systems.

    you have an air pump, that needs to be sealed.

    you have a source of fuel and a way to mix it with the air being pumped.

    you have an ignition source timed to go off at the right point in the cycle.
    Rockin_Roll likes this.
  17. Rockin_Roll

    Rockin_Roll New Member

    After priming via the intake, it kicked liked it was gonna start, than immediately died. Assuming it might be a fouled carb, I removed the filter cover, and the darn filter was drenched with fuel/oil. I mean soaked. And ever after removing it, it still weeped oil to the inner edge. I wipe it away, come back 15, 20 minutes, oil was still collecting in curve of the inlet. Then noticed there were drops of fuel on the floor, and had been there for some time, just hadn't taken notice. So there's no saying how long this puppy's been spitting oil. Could this be at the heart of my problem all along?

    Now I see on the net that carbs aren't all that costly, so thought of just buying a new one, but since the whole point of this exercise is educational, I decided to disassemble and clean the thing following the steps outlined here on the forum and you tube and see what I can learn, and maybe in the process just might get my bike to fire up.

    One last thing. In unhooking the fuel line, do I drain the tank completely, and start off with a fresh fuel/oil mixture? Or is that necessary. Surely you vets must have a system, cause seems kinda unwieldy uncapping the line, recapping and hooking it up again without making a god-awful mess. Just don't want to get oil into some place maybe it shouldn't be...
    Last edited: Nov 14, 2015
  18. crassius

    crassius Well-Known Member

    I usually just turn off the petcock if I know the fuel is good, to drain tank, I just put a long hose onto petcock and let it drain into a jug on the floor.
    Rockin_Roll likes this.
  19. KCvale

    KCvale Motorized Bicycle Vendor

    Just to be clear as to the difference between a 2-stroke and a 4-stroke engine, you can't 'prime' a 2-stroke with liquid fuel.

    Spray starter will work, but otherwise most of it just puddles in the bottom of crankcase and you don't want that.

    On an NT carb, all the primer button does is hold the float bowl down to fill it after is sits awhile to fill it.
    Keep holding it down and fuel is going to flow either out the filter if your carb is tileted back, or into the engine if it's tiled forward.

    Is your carb level?

    The entire fuel system is gravity based.
    You simply need your carb as level to ground as possible to function.

    If carb is level then it's just a float bowel adjustment but you can only adjust so far.

    I do all my fuel system work outside, no exceptions as I live here and gas on carpet is not friendly.

    You shouldn't need to worry about fuel quality yet.
    But for prepping carb removal I like to have it running and just shut off fuel flow until the engine dies.

    You can't do that, so just turn off flow, pinch the gas line where it enters the carb, disconnect that and secure the gas line end end as high as you can above the gas tank.

    Got a level side pic of engine and carb?
    I have a hunch that's your problem.
  20. bakaneko

    bakaneko Active Member

    I hope you fixed it by now, m8. But, just in case, I wanted to ask a simple question: have you disconnected the kill switch? My bike was running great and then didn't turn over or would sputter out quickly from start. It turns on the kill switch was malfunctioning and cutting my engine out. If you haven't try just disconnecting the kill switch.
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