D
duivendyk
Guest
There is still rampant confusion about the ignition system of HT engines.This tutorial might be useful reading for folks trying to get their bearings.
Inside the engines is a flywheel generator that produces a ac (positive& negative going output) pulse,from the generator coil at the appropriate time.
Three leads are connected to this coil,one end of the winding on it is connected to the Blue lead,this is the output lead that needs to be hooked up to the blue input of the CDI unit (about this later).The Black lead is the other end of the coil,it is what EE's call the "common" or ground,although strictly speaking it does not have to be connected to the engine or bike frame.Then there is the infamous White lead,this is tap on the coil fairly close to the bottom end (the black wire).This produces a much smaller ac pulse and can be used to power a light (if you're careful),the output depends on the engine speed,it's better to leave it alone though,it's a potential source of trouble.
The CDI unit ,it receives the ac pulse from the generator(blue&black wire) and produces a high voltage pulse to the plug to fire it.It appears to be underdesigned and frequently fails (get some backups).High voltages and moisture don't get along at all.Repackage it in a box and seal it with RTV (only when it is DRY!!.)
The kill switch is used to kill the input to the CDI unit,this can be done either by shorting the input,that is hooking up the switch between the blue and the black leads or by opening up the input to the CDI, that is hooking up the switch between the blue lead from the engine and the one from the CDI input.You could do both if you want a "secret" disable capability.Some people have expressed concern that they could "fry" the coil with the short,those concerns are misplaced,there is around 300 ohms in the winding and the amount of heating of it by the short circuit current,for the short duration until the engine stops is quite small.
The coil output at the blue wire is a healthy pulse, a few hundred volts !,under the right conditions it could kill you,treat it with respect.This voltage is at the kill switch no matter how you hook things up.The best way would be to have the switch close to the CDI unit,the CDI box would be a good place for it.The kill switch should be a high quality sealed switch.I am not a fan of using the frame for ground returns,it allways entails multiple questionable frame ground connections for the black wire,at the switch at the CDI unit or at the engine.I would prefer a single frame ground at the CDI or the engine and run the black wire to the switch.If you want to use the series switch configuration the blue connection has to be run from the engine to the switch and then back from the switch to the CDI.In this arrangement the blue leads are carrying pulse current during normal operation.It is advisable to minimize the EMI due to magnetic fields generated by these currents by using a twisted pair.This is why I'm not all that thrilled by this scheme and prefer the shorting method.
Trouble shooting,invest in a Multimeter, you can get one for around $10,it's money well spent.
1)Engine has quit, has run previously,reason to suspect ignition.Disconnect blue wire at engine,measure resistance to black wire, should be around 350 Ohms, if open circuit coil bad.If open circuit, operate kill switch (ONLY if shunt mode is used) .If open circuit disappears,coil bad between white and black wire (opened up).This can happen if light output was shorted or overloaded and a portion of the coil has been fried.May still be able to run engine but function of kill switch is reversed.
2) Coil appears OK,disconnect kill switch at engine or CDI (shunt mode).Test engine,no go, either CDI or fuel supply.If switch in series mode get rid of blue connections to switch and connect blue wire from engine directly to CDI & test engine
3) Using the white wire,it had best be left alone&taped up,if you feel compelled to use it take at least the precaution of wiring a 1 Amp fuse into the connection,that keeps you from frying the generator coil if you had a short,if you had one you might nor be able to get started but once running it would not necessarily cause the engine to quit,at least not until you had managed to fry the coil
4) using the white wire to charge a battery,it should be no problem charging a 6 V leadacid battery,the trick will be to keep it from overcharging.If I had more info about the coil resistance beween the white&black wires and had measured open circuit output (ac) voltages at idle&at speed it would not be all that hard for me to come up with a simple circuit that could be built from readily available parts, to take care of the battery charging.
5) Testing sparkplugs.I have stated before that I think the CDI unit is a marginal proposition especially the output pulse transformer.When testing plugs keep the body of the plug GROUNDED !,to prevent zapping it. Good luck.
Inside the engines is a flywheel generator that produces a ac (positive& negative going output) pulse,from the generator coil at the appropriate time.
Three leads are connected to this coil,one end of the winding on it is connected to the Blue lead,this is the output lead that needs to be hooked up to the blue input of the CDI unit (about this later).The Black lead is the other end of the coil,it is what EE's call the "common" or ground,although strictly speaking it does not have to be connected to the engine or bike frame.Then there is the infamous White lead,this is tap on the coil fairly close to the bottom end (the black wire).This produces a much smaller ac pulse and can be used to power a light (if you're careful),the output depends on the engine speed,it's better to leave it alone though,it's a potential source of trouble.
The CDI unit ,it receives the ac pulse from the generator(blue&black wire) and produces a high voltage pulse to the plug to fire it.It appears to be underdesigned and frequently fails (get some backups).High voltages and moisture don't get along at all.Repackage it in a box and seal it with RTV (only when it is DRY!!.)
The kill switch is used to kill the input to the CDI unit,this can be done either by shorting the input,that is hooking up the switch between the blue and the black leads or by opening up the input to the CDI, that is hooking up the switch between the blue lead from the engine and the one from the CDI input.You could do both if you want a "secret" disable capability.Some people have expressed concern that they could "fry" the coil with the short,those concerns are misplaced,there is around 300 ohms in the winding and the amount of heating of it by the short circuit current,for the short duration until the engine stops is quite small.
The coil output at the blue wire is a healthy pulse, a few hundred volts !,under the right conditions it could kill you,treat it with respect.This voltage is at the kill switch no matter how you hook things up.The best way would be to have the switch close to the CDI unit,the CDI box would be a good place for it.The kill switch should be a high quality sealed switch.I am not a fan of using the frame for ground returns,it allways entails multiple questionable frame ground connections for the black wire,at the switch at the CDI unit or at the engine.I would prefer a single frame ground at the CDI or the engine and run the black wire to the switch.If you want to use the series switch configuration the blue connection has to be run from the engine to the switch and then back from the switch to the CDI.In this arrangement the blue leads are carrying pulse current during normal operation.It is advisable to minimize the EMI due to magnetic fields generated by these currents by using a twisted pair.This is why I'm not all that thrilled by this scheme and prefer the shorting method.
Trouble shooting,invest in a Multimeter, you can get one for around $10,it's money well spent.
1)Engine has quit, has run previously,reason to suspect ignition.Disconnect blue wire at engine,measure resistance to black wire, should be around 350 Ohms, if open circuit coil bad.If open circuit, operate kill switch (ONLY if shunt mode is used) .If open circuit disappears,coil bad between white and black wire (opened up).This can happen if light output was shorted or overloaded and a portion of the coil has been fried.May still be able to run engine but function of kill switch is reversed.
2) Coil appears OK,disconnect kill switch at engine or CDI (shunt mode).Test engine,no go, either CDI or fuel supply.If switch in series mode get rid of blue connections to switch and connect blue wire from engine directly to CDI & test engine
3) Using the white wire,it had best be left alone&taped up,if you feel compelled to use it take at least the precaution of wiring a 1 Amp fuse into the connection,that keeps you from frying the generator coil if you had a short,if you had one you might nor be able to get started but once running it would not necessarily cause the engine to quit,at least not until you had managed to fry the coil
4) using the white wire to charge a battery,it should be no problem charging a 6 V leadacid battery,the trick will be to keep it from overcharging.If I had more info about the coil resistance beween the white&black wires and had measured open circuit output (ac) voltages at idle&at speed it would not be all that hard for me to come up with a simple circuit that could be built from readily available parts, to take care of the battery charging.
5) Testing sparkplugs.I have stated before that I think the CDI unit is a marginal proposition especially the output pulse transformer.When testing plugs keep the body of the plug GROUNDED !,to prevent zapping it. Good luck.
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