Need a CDI...

Discussion in '2-Stroke Engines' started by PhoobarID, Apr 30, 2010.

  1. PhoobarID

    PhoobarID Member

    Took the 66cc out for it's virgin ride Monday afternoon. Made it about 9 miles with bugs in my teeth & wouldn't run at all. After pedaling it about 1/2 mile home...took out the plug & found I was getting no spark. Think my buddy wired up the kill switch to the CDI it was fried.

    If anyone's got a good used CDI with the steps on wiring it up correctly & want to get rid of it for about $5 or so (new ones with shipping run about $25 & I just don't have that kind of money right now)..let me know in PM.


  2. Al.Fisherman

    Al.Fisherman Active Member

    Before you invest in a CDI, check the voltage that the magneto is putting out if any. If you don't have a test light/volt meter I can tell you how to make a easy and CHEAP test light. 1 bulb and a few feet of thin wire, solder or tape.
  3. KCvale

    KCvale Motorized Bicycle Vendor has CDI's for $10.
    Did you check the 2 wire connections from the CDI to the motor?
    One coming loose is very common.
    Also, just disconnect the kill button from the white magneto motor wire in case it is shorting.
  4. PhoobarID

    PhoobarID Member

    How do I actually test it without being able to get the bike started? What readings are there supposed to be & in what range if someone has a meter?
  5. PhoobarID

    PhoobarID Member

    Looked at that source first. The bad thing about them is their cheap prices...but high shipping costs. That costs as much or more than the part itself. May look on Ebay to see what I can come up with.

    That actually happened...but put them back together & took some pliers & clasped the connector tight.

    For some buddy had the white wire hooked to the block...because he said it needed a ground. Unhooked it when this started happening & still nothing.

    Do you have detailed directions to wire these devices up with what wires go where? I have the black to to blue...but am unsure about the kill switch. If I don't hook up the kill switch to test it...will that allow me to see if either part is bad?
  6. Al.Fisherman

    Al.Fisherman Active Member

    This thread now needs to be moved to the 2 cycle section. In the meantime....There are a number of ways. Peddling the bike, being towed, coast down hill and even turning the engine over with a drill/socket (removal of chain is required, don't depend on disengagement of the clutch). Remove the plug from the head and leave in the cap and grounded even if you need to wire the threads to ground. Voltage should be around 6-7 volts. Check blue to black and white to black. I use a 6V or a 12V test light. You can make one out of a 6 V (best) or 12 volt bulb like what goes in a side marker or tag light. Very low watt bulb.
    Last edited: May 1, 2010
  7. Al.Fisherman

    Al.Fisherman Active Member

    White wire to ground a no no, it's a hot wire. That wire carries 6-7 volts and grounding can and may of damaged the coil. Check output of coil tho.

    Blue wire is hot from mag to blue on the CDI, black is grounded at mag and hooks up to the black on the CDI. The white wire is a hot output from the mag that they say is for lights, if you believe it.... specialty light needs to be used as most 6 volt lights draw too many amps.

    Eliminating the kill switch will eliminate switch problems (if any) while testing.
    Last edited: May 1, 2010
  8. PhoobarID

    PhoobarID Member

    I suspected this...but being my buddy has done this before...thought he would get it right. Since I'm using rubber tubing around the frame at the mounts to lessen the vibration on my wrists/body & to protect the paint...I think he thought I needed a ground to the engine. Put a pix of the build with the message & in my album.

    If I'm not powering lights or some other device...that white wire is just something which doesn't get hooked up?

    Will do that. Think I have a test light out in the pickup or my toolbox. They're cheap enough as it is if I don't. Do I check the wires going out to the CDI or open up the cover? If inside the cover...where would I put the probe?

    Would this have damaged the wired U-shaped magneto as well?

    Attached Files:

  9. KCvale

    KCvale Motorized Bicycle Vendor

    The white motor wire is the direct magneto 7.5V AC output when the motor is running. It is unregulated, and voltage varies with motor RPM, the faster the motor turns, the more power it puts out.

    The blue wire to the CDI is please correct me if I am wrong a magneto voltage pulse send when the piston is whatever the degrees before top dead center is to fire the plug.

    The black wire is the ground for the motor and this circuit.

    All the kill switch does, with it's green frame wire to white magneto wire, is ground the magnetos output, killing input to the CDI along with it.

    It is amazing you were able to run the motor with the white wire to bike frame.
    Not just the motor mounting, but the clutch and throttle cables and chain needed to be completely isolated from the motor as well as would serve as a motor to bike ground connection.

    Hahah, in fact, your whole bike had to be "energized" with voltage when the motor ran, and what ran it (the ignition system) was on it's own isolated circuit. If it actually did run that way it has to be one for the books.

    Chances are you toasted the magneto.
    A meter is the best to tell as a magneto coil does have some resistance, but a test light should do the test.
    Just ground one end to the MOTOR, and hook the white wire to other end.
    The light should light if it's good.
  10. PhoobarID

    PhoobarID Member

    Sounds like anything other than battery powered lights is the way to go without spending some change on some sort of regulator setup. If that's the case...may as well get a motorcycle.

    Not sure if I'm correct or not...but when you hook up the wires to the CDI...that's where your ground comes from...rather than using the same setup with a separate huge negative wire for your ground on a car.

    Do I use the white wire for anything other than powering a light or something else which needs the power? Would I just cap or tape it off if I don't want to use it?

    I think my buddy was thinking the engine wouldn't be grounded without that wire being attached.

    With my current build...are all these isolated?

    It made it about 9 miles with the bronze looking tail pipe to prove it.;)

    Wasn't sure if it was the magneto or CDI...but those are the only things which provide the power to run the engine. Am so very happy I didn't have a battery in the circuit or would be suffering from acid burns when it exploded. Seen that happen before & it's not pretty.

    Nice...will do that tomorrow since it's raining. Totally expect to find it blown.
  11. Al.Fisherman

    Al.Fisherman Active Member

    You will hear so many ways to wire these things up. The blue yes gives a pulse from the magneto due to the magnet spinning inside it. Unless you either have or have plans to try and hook up lights with the white wire....remove it at the magneto. It is of no use and with removal won't cause problems down the road. How I have my kill switch hooked up on all builds that I have done is to run the wires (mine had 2 long wires) from the kill switch (supplied on switch) down to the CDI. I attach one wire to the blue (hot) and the other to black (Ground). It doesn't make any difference which wire color on the switch goes to what wire color on the CDI. Hooked up this way you are grounding the pluse lead (blue wire) directly to ground, thus cuts off power to the CDI.
  12. PhoobarID

    PhoobarID Member

    Got nothing off the was able to get some spending money yesterday. Have the am going to replace the units. Should be on the road by this weekend.

    Want to thank everyone for spelling out exactly how to wire these devices up. Sure makes a BIG difference when getting them road worthy.
  13. PhoobarID

    PhoobarID Member

    Just ordered the CDI & magneto from Kings for $31 US. Should be here by Thursday & should be on the road by Friday evening to try to break in the 1st gallon by Saturday evening...if it's not raining.
  14. KCvale

    KCvale Motorized Bicycle Vendor

    Correct. The white wire is just raw magneto voltage.
    The kits use it for the kill button, but as mentioned you can hook the kill button between the two magneto wires for the same result.

    So yes, you can just tape it off, or you can indeed use it to power lights.
    The trick is if you draw more than 1/2 an amp there won't be enough voltage to power the CDI to spark and the motor will die.

    I haven't made one yet but this should work fine for a constant 6V DC source.

    All you need is one 50ยข 10V 500mA diode from Radio Shack and a 6V NiCad battery pack.
    You could just 4 C or D batteries in a holder, or an old electric RC car battery pack.

    Just put the diode in line with the white wire to the + side of the pack, and ground to the - side.

    The single diode acts as a half wave rectifier and turn the AC into pulsed 6V DC.
    You could use 4 diodes for a full wave, but using all the AC wave could end up drawing more than 500mA and kill your engine.

    In short, whenever the motor is running the battery is charging.
    Just hook your 6V lights right up to the battery. They should even work with the motor off until the battery is drained, but otherwise work just dandy even they draw an amp.
    The battery will make up the difference, and even when the battery dies, chances are you still won't be able to draw 1/2 an amp with half wave, the lights will just dim.
    Last edited by a moderator: Dec 18, 2015
  15. PhoobarID

    PhoobarID Member

    Got 'er done...

    Put the new electrical system put on the bike & went for a 6-7 mile ride this evening. Even the kill switch works like a dream.

    The worst part...the bad roads & rain gutters to channel the rain at the intersections. My kidneys feel like George Sr....Muhammad Ali went 30 rounds with me for 10 minute rounds.
  16. Al.Fisherman

    Al.Fisherman Active Member

    Very good...what we do to have fun...oh well
  17. PhoobarID

    PhoobarID Member

    Oh yeah!!! Even did it by myself from what all of you told me. Less than an hour total & was on the street.
  18. KCvale

    KCvale Motorized Bicycle Vendor

    Well, for some of us including me, MB's are our only form of practical, cheap, legal, and independet form of transportaion.

    So Poobar, did you run the kill button to the CDI and isolate the white magneto wire?

    Quick question...
    I haven't replaced a magneto, did you have to messing with timimg? or did it just pop back in with guides to set it properly for you?
  19. PhoobarID

    PhoobarID Member

    It will be that for me this summer & beyond. For instance...ran to the library (2 miles 1 way) & to see a friend of mine on the other side of town (3-4 miles 1 way). Put about 7-8 miles on it last night.

    Eventually...want to put the 4-stroke I used to have on it back on it with a belt drive. That Grubee clutch is a POS & works the opposite way of the 2-stroke & motorcycles. This 2-stroke clutch actually gives me the feel of when I used to ride motorcycles. Except for the speed...feels very close to my 1st motorcycle I ever rode.

    What I did was grab a pair of scissors & cut it off at the solder on the coil. Ended up using the wire to connect the kill switch to the CDI because the included wire was too short to make the connection. Covered it all in electrical tape & as soon as my paycheck comes in...will be getting some shrink wrap & some silicone...along with some cable ties. Money is short right I'm using tape & such to keep stuff in place. Not as nice as I want...but it does work for the short term.

    You will see what I did from the CDI from the pix.

    Disconnected the 4 screws...making sure I made a mental note where the black wire hooked to. Actually getting the old coil out of there was harder than I was expecting...due to the magnet. Putting it back in...put my black wire on the correct screw & hand-tightened the first screw a few turns to hold the screw & coil in place. Taking another of the screws...went the opposite corner & started that one. Just like changing the spare on the went into place without a problem.

    As for the timing...did nothing with this. Just pulled out the old coil & put in the new one. If I can do it & in under an hour...anyone can do it. Just 4 wires & you're good to go.

    The only advice I would have for you is to take it nice & slow. That magnet is a good 1. Make sure you have no electronics on you as well. They might not work after working around that magnet.

    Attached Files:

  20. Al.Fisherman

    Al.Fisherman Active Member

    Timing is set with a key on the shaft that the magnet is on. The key goes between the crankshaft and magnet. No timing adjustment.