nads.com wrote: 1985 honda big red. No spark. Exciter coil has50+ ac volts.
Trikes will get you killed.
nads.com wrote: Pulse coil zero. Took off engine cover and the magnet on the outside of the wheel for the pulse coil was dead or near. From ebay pics, it looked like a magnet used to sit on top the raised steel block i mistook for a magnet. I put my own magnet on it and now how have apulse thats .3 or +. Thats what was qouted as the spec.
Do you have photos? Usually the magnet on the rotor passes by the stationary pulse coil. Is that what you have now? How do you know if you have the magnet polarity correct? Have you tried both ways? Do you know if the poles are facing the correct orientation (not just polarity, but actual pole directions as they pass the pulse coil)? You probably need to somehow get a factory magnet to know how it is oriented with regards to poles.
This link will show how to determine a magnet's north/sout polarity.
gpzweb.s3-website-us-east-1.amazonaws.co.../PickupAndRotor.html
nads.com wrote: Still no spark and 2v to the charge wire to the coils.
This pulse happens once per rotation? Measured with a regular DC voltmeter? DC Voltmeters measure *average* voltage, so it is difficult to judge what the actual *peak* voltage spike was to the coils... but 2v seems very low, even for an average. This could mean the capacitor ("C" in "CDI") may be bad, or the trigger is happening at the wrong time (due to wrong magnet polarity or orientation), or the SCR is bad, or other things I haven't thought of.
nads.com wrote: My question to all is.... Is .3v enough to trigger or open the gate of an scr, or thyristor, or whatever is in the cdi?
0.3v seems pretty low. But again, are you using a typical DC voltmeter? If so, then you don't really know what the peak pulse was. Also, the pulse could be AC, in which case the .3v DC reading is almost meaningless.
nads.com wrote: Is the scr polarity sensitive and wont turn on if i installed my magnet with n and s poles opposite the orginal magnet?
SCR's have a polarity for their main current, but I assume you are asking about their trigger signal. The trigger needs to be the correct polarity to trigger the SCR. If the trigger signal is not rectified (normally they are not), then the pulser signal is AC. So if the polarity is wrong, the pulse timing may be off, and the peak value may be different from what is expected, so it may or may not trigger depending on the details of the signal.
nads.com wrote: And if polarity of the pulse is now reversed can it burn out the new cdi.
Typical CDI systems for dirt bikes are crude, and there is not a whole lot to them. So normally, having the polarity wrong should not harm the SCR.
You can possibly test the CDI system by using a 1.5v battery in series with a 100 ohm resistor.
Disconnect the pulser, and put the 1.5v battery and resistor in its place. Rotate the crank a few times and connect the battery to the CDI input. This should trigger the CDI and you should see a spark.
The battery negative goes to ground. The positive goes to the resistor, and the resistor feeds the CDI module (where the pulser would connect). If both wires of the pulser went to the CDI module, then don't ground the battery. The battery negative will go to the second wire, and you have to try the battery in both directions to get the polarity correct.
If that works, then there is some problem with the pulser and/or magnet.