A Simple Motorcycle Electronic Ignition Replacement.
Although these are guides, you must never read this, nor even consider building such devices nor act upon this information. This is because the dogs of law lie around every corner, and everyone should just live a quiet, pastoral life for fear of litigation. (As lawyers get richer, society gets poorer.) If you want freedom, then always vote to keep lawyers and assholes out of politics.
There are many motorcycles which use electronic ignition systems and all have one thing in common, the black box costs a fortune.
For the poor in Britain, or those with small bikes, the costs of replacement can be minimal, as they all have the same basic design. The following simple modification has been run quite happily on Honda NS125, KTM 125 and Yamaha TZR125. All had no electronic ignition systems other than the contents of the generator on the engine. Most wires were burnt flush with the blackened crankcase. This will also work on many larger and smaller machines, with or without wheels.
A little theory. Four strokes (four cycle, Otto cycle,) engines, when spinning fast, need the spark to happen many degrees before the piston reaches the top of the cylinder. This allows time for the flame front to pass through the fuel and air mixture in the cylinder to be at its full potential as the piston begins to descend on the power stroke. But at low speeds, the flame front still happens at the same speed, so at low revs it is therefore necessary for the spark to happen a little later, so the maximum power in the fuel and air mixture still happens as the piston begins to descend. To allow this to happen, most four stokes have an 'advance and retard' unit, which senses the engine speed and times the spark at the right place according to the engine revs.
The Honda C90, ('stepthru' as its normally called) does not have an advance unit, and because its a small engine with plenty of flywheel, it can run happily without an advance and retard unit. As many C90's are scrapped each year, there is a glut of C50/70/90 CDI units and these are the core of this monograph. Many small four strokes can also run happily without an advance and retard unit. But larger four stokes cannot and may damage the piston and crank bearings if the timing is not ideal.
Therefore most four strokes need an advance and retard unit. On early machines, up to around 1985's this is a centrifugal mechanical device, but on modern machines, this is often incorporated in the electronics box. The mechanical designs are usually easy to modify. The latest designs are not easy to do and not discussed here. So if you do not have a mechanical advance unit, then your machine will have to look elsewhere for a solution. Some possible options are described later.
Although these are guides, you must never read this, nor even consider building such devices nor act upon this information. This is because the dogs of law lie around every corner, and everyone should just live a quiet, pastoral life for fear of litigation. (As lawyers get richer, society gets poorer.) If you want freedom, then always vote to keep lawyers and assholes out of politics.
There are many motorcycles which use electronic ignition systems and all have one thing in common, the black box costs a fortune.
For the poor in Britain, or those with small bikes, the costs of replacement can be minimal, as they all have the same basic design. The following simple modification has been run quite happily on Honda NS125, KTM 125 and Yamaha TZR125. All had no electronic ignition systems other than the contents of the generator on the engine. Most wires were burnt flush with the blackened crankcase. This will also work on many larger and smaller machines, with or without wheels.
A little theory. Four strokes (four cycle, Otto cycle,) engines, when spinning fast, need the spark to happen many degrees before the piston reaches the top of the cylinder. This allows time for the flame front to pass through the fuel and air mixture in the cylinder to be at its full potential as the piston begins to descend on the power stroke. But at low speeds, the flame front still happens at the same speed, so at low revs it is therefore necessary for the spark to happen a little later, so the maximum power in the fuel and air mixture still happens as the piston begins to descend. To allow this to happen, most four stokes have an 'advance and retard' unit, which senses the engine speed and times the spark at the right place according to the engine revs.
The Honda C90, ('stepthru' as its normally called) does not have an advance unit, and because its a small engine with plenty of flywheel, it can run happily without an advance and retard unit. As many C90's are scrapped each year, there is a glut of C50/70/90 CDI units and these are the core of this monograph. Many small four strokes can also run happily without an advance and retard unit. But larger four stokes cannot and may damage the piston and crank bearings if the timing is not ideal.
Therefore most four strokes need an advance and retard unit. On early machines, up to around 1985's this is a centrifugal mechanical device, but on modern machines, this is often incorporated in the electronics box. The mechanical designs are usually easy to modify. The latest designs are not easy to do and not discussed here. So if you do not have a mechanical advance unit, then your machine will have to look elsewhere for a solution. Some possible options are described later.
Two Strokes.
Two stroke (two cycle) engines, because of their design, do not need the spark to advance with increasing engine revs. Tick over on a two stroke works quite happily at the fully advanced setting used for full power, and as such, there is no need to have an advance and retard unit. This makes it very easy to fit almost any electronic ignition unit.
Typical set-up.
Inside the basic flywheel rotor are usually two main coils. One coil is fairly large and supplies about fifteen to thirty volts AC to the rectifier for the battery and lights. The other coil is a smaller, more finely wound coil to supply a hundred or so volts to the CDI unit. Outside, or sometimes inside is a small, finger tip sized pulser coil, which triggers the CDI at the correct time for the spark.
This picture shows a C90 rotor with the pulser interrupter as a piece of metal sticking out on the outer edge, which causes the timing pulse at the right place, and the pulser is the black lump between the rotor and stator. Lying flat is the stator plate with the pale lighting and dark CDI generator coils.
There are four or more magnets inside the rotor (it rotates), such that as they pass the stator (static) coils, they induce a changing north - south - north - south alternating magnetic field in the iron plates of the coils, thereby generating electricity in the copper coils of wire.
As can be seen, the four poles at the ends of the coils means that the magnets in the rotors are four, so the N-S-N-S field flows strongly through the iron cores. This is acceptable for a low power machine, but sometimes a little more electrical power is needed in such a small space, so six poles can be used, with six rotating magnets. My old Ducati V twin used about twenty permenanat magnets.
Now we are six. The black and white picture shows another popular arrangement, where the lighting coils are the five coarsely wound coils, while the generator is the obviously different one nearest the viewer. Again the pulser is outside. You will also notice that as a six pole stator, the rotor should have six magnets. You can just make out the size and layout of the six magnets inside the rotor.
Assuming a badly damaged machine.
You may be looking at a burnt out wreck of an engine, I often do, as they are the only ones I can afford. Remove the rotor. Either use the correct tool called a 'puller', or borrow one and always return it in perfect condition. If you do not have a puller, then uncrew the central nut on the flywheel until it is flush with the end of the crankshaft.
With a friend, place two tyre levers (tire irons) behind the back of the flywheel, so that they place a pulling force outwards, levered carefully against the crankcase. Hit the central nut sharply with a small hammer until the flywheel loosens. By placing the nut level with the end of the crankshaft, then the hammering will not damage the crankshaft threads. Do not allow the tyre levers to dent the crankcase. A single, firm, sharp tap should suffice to release most flywheels. Remove the nut and flywheel.
Inspect the wiring to each coil and make a note of the colours to each. Locate the fine wound high voltage coil inside the flywheel generator and inspect the components carefully. Where any wire to the wiring loom is damaged, simply desolder and replace with a new wire. The preferred colours are mentioned below. Ensure the insulating sleeve is securely replaced and will not slide off to expose the bare soldered joint. I usually remove the backing plate the bike, be it a PE suzuki enduro, TZR road racer, or my own specials, then inspect each coil and if suspect, repair as deemed suitable, taking the opportunity to use the old Honda C90 wring loom to fit new wires exiting from the engine casing.
Eventually you will have nice new wires exiting the engine, an earth wire, and a wire or two from the high voltage coil, a wire or two from the heavier coil for the lighting and battery charging, plus a wire or two from the small pulser unit. In some cases, the small pulser coil and the high voltage coil may not be earthed, so will have two wires each, one from each end of their coil of copper wire. As these components normally use an earth, then this can be done by extending the wires and terminating them to an earth tag outside the crankcases. If this does not work, then they are probably connected inside the original CDI unit, but for the C90 unit, they can be earthed.
The C90 unit.
The spark from a C90 ignition will jump the gap in a 50cc to a 1500cc bike, as all spark plugs are essentially the same. There is no need to have a big CDI unit for a big bike. (If the cost of four C90 set-ups is one tenth the cost of the genuine article, then at least have a try at fitting four sets.)
The electronic ignition of many motorcycles and similar machines with electronic ignition can be run using the cheapest and most easily available electronic ignition in the world. Honda C90 parts are available from all second hand bike dealers and breakers, usually for a few pounds, always try to get the wiring loom as well, or at least the part of the wiring loom between CDI and engine. The parts needed are the CDI unit, the wiring loom connector and a foot or so of attached wire, and the ignition coil. I often use the C90 stators inside the flywheel for a supply of suitable copper wire for rewinding this set - up onto other machines.
The simple and commonly available Honda C90 CDi unit works very well with most small two strokes. I can also work with many four strokes which use a mechanical advance and retard unit. To check for a mechanical advance unit, it looks like a set of bob weights restrained by small springs which will fly out when running. This is common on most four strokes with points and can also be a conversion for some older machines. See later.
Two stroke (two cycle) engines, because of their design, do not need the spark to advance with increasing engine revs. Tick over on a two stroke works quite happily at the fully advanced setting used for full power, and as such, there is no need to have an advance and retard unit. This makes it very easy to fit almost any electronic ignition unit.
Typical set-up.
Inside the basic flywheel rotor are usually two main coils. One coil is fairly large and supplies about fifteen to thirty volts AC to the rectifier for the battery and lights. The other coil is a smaller, more finely wound coil to supply a hundred or so volts to the CDI unit. Outside, or sometimes inside is a small, finger tip sized pulser coil, which triggers the CDI at the correct time for the spark.
This picture shows a C90 rotor with the pulser interrupter as a piece of metal sticking out on the outer edge, which causes the timing pulse at the right place, and the pulser is the black lump between the rotor and stator. Lying flat is the stator plate with the pale lighting and dark CDI generator coils.
There are four or more magnets inside the rotor (it rotates), such that as they pass the stator (static) coils, they induce a changing north - south - north - south alternating magnetic field in the iron plates of the coils, thereby generating electricity in the copper coils of wire.
As can be seen, the four poles at the ends of the coils means that the magnets in the rotors are four, so the N-S-N-S field flows strongly through the iron cores. This is acceptable for a low power machine, but sometimes a little more electrical power is needed in such a small space, so six poles can be used, with six rotating magnets. My old Ducati V twin used about twenty permenanat magnets.
Now we are six. The black and white picture shows another popular arrangement, where the lighting coils are the five coarsely wound coils, while the generator is the obviously different one nearest the viewer. Again the pulser is outside. You will also notice that as a six pole stator, the rotor should have six magnets. You can just make out the size and layout of the six magnets inside the rotor.
Assuming a badly damaged machine.
You may be looking at a burnt out wreck of an engine, I often do, as they are the only ones I can afford. Remove the rotor. Either use the correct tool called a 'puller', or borrow one and always return it in perfect condition. If you do not have a puller, then uncrew the central nut on the flywheel until it is flush with the end of the crankshaft.
With a friend, place two tyre levers (tire irons) behind the back of the flywheel, so that they place a pulling force outwards, levered carefully against the crankcase. Hit the central nut sharply with a small hammer until the flywheel loosens. By placing the nut level with the end of the crankshaft, then the hammering will not damage the crankshaft threads. Do not allow the tyre levers to dent the crankcase. A single, firm, sharp tap should suffice to release most flywheels. Remove the nut and flywheel.
Inspect the wiring to each coil and make a note of the colours to each. Locate the fine wound high voltage coil inside the flywheel generator and inspect the components carefully. Where any wire to the wiring loom is damaged, simply desolder and replace with a new wire. The preferred colours are mentioned below. Ensure the insulating sleeve is securely replaced and will not slide off to expose the bare soldered joint. I usually remove the backing plate the bike, be it a PE suzuki enduro, TZR road racer, or my own specials, then inspect each coil and if suspect, repair as deemed suitable, taking the opportunity to use the old Honda C90 wring loom to fit new wires exiting from the engine casing.
Eventually you will have nice new wires exiting the engine, an earth wire, and a wire or two from the high voltage coil, a wire or two from the heavier coil for the lighting and battery charging, plus a wire or two from the small pulser unit. In some cases, the small pulser coil and the high voltage coil may not be earthed, so will have two wires each, one from each end of their coil of copper wire. As these components normally use an earth, then this can be done by extending the wires and terminating them to an earth tag outside the crankcases. If this does not work, then they are probably connected inside the original CDI unit, but for the C90 unit, they can be earthed.
The C90 unit.
The spark from a C90 ignition will jump the gap in a 50cc to a 1500cc bike, as all spark plugs are essentially the same. There is no need to have a big CDI unit for a big bike. (If the cost of four C90 set-ups is one tenth the cost of the genuine article, then at least have a try at fitting four sets.)
The electronic ignition of many motorcycles and similar machines with electronic ignition can be run using the cheapest and most easily available electronic ignition in the world. Honda C90 parts are available from all second hand bike dealers and breakers, usually for a few pounds, always try to get the wiring loom as well, or at least the part of the wiring loom between CDI and engine. The parts needed are the CDI unit, the wiring loom connector and a foot or so of attached wire, and the ignition coil. I often use the C90 stators inside the flywheel for a supply of suitable copper wire for rewinding this set - up onto other machines.
The simple and commonly available Honda C90 CDi unit works very well with most small two strokes. I can also work with many four strokes which use a mechanical advance and retard unit. To check for a mechanical advance unit, it looks like a set of bob weights restrained by small springs which will fly out when running. This is common on most four strokes with points and can also be a conversion for some older machines. See later.
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