I devised this system when the stator on my Honda XR-100 got so weak that it couldn't power the spark plug, preventing the engine from running. The stator on my model happened to be discontinued, and I didn't want to buy a used one for over $100 when this particular stator is known for being weak and prone to failure.
The stator coil generates the power for the spark plug and other accessories on small engines Without a stator there would be no spark at all, meaning the engine won't run. While a stator is dying, it can produce a weak spark, causing the engine to miss or run poorly. Symptoms are often worsened as the engine warms up.
Step 1: Required Materials
This needs to be a fairly heavy duty coil. I previously tried using two universal coils intended for small engines. They both literally blew up from the heat. (I guess they're not designed for a continuous 12 volts?) I found that the (older) canister type ignition coil designed for cars work for this application and don't get hot or blow up. I bought this no name one off Amazon for about $15.
12 Volt battery:
Any 12 volt battery will work. This is the lead acid type used for car batteries. They sell small ones for use in dirt bike starters, security system back up power supplies, etc. I bought a generic one off Amazon for about $18.
See the possible methods on the last page. $0-100.
Any capacitor intended for ignition systems will work. (I don't know the technical specification). I used the one that was one that was part of the original ignition system on my dirt bike.
This is to protect the ignition coil from receiving too much power. Use a 2 ohm resistor rated in the neighborhood of 100 watts of power. I bought a generic one for about $5 off ebay.
On Off Switch:
You can use the one that came with your engine as long as it's not the kind you have to hold down. My dirt bike had the hold down style so I bought a $5 toggle switch from home depot.
Flywheel Removal Tool:
They sell a universal one for most small engines on various websites. I got mine for about $10 on Amazon.
Insulated Wiring + Alligator clips + Sandpaper (optional)
I used 18 gauge insulated magnet wire. I would cut sections off a spool to the required length, then sand the insulation off the ends and attach alligator clips. The way you go about wiring is a personal preference, so if you want to buy ready to use wires with alligator clips, or even solder all connections without clips that's your call.
This is used to measure resistance and to check continuity. While not required, it is helpful to have for troubleshooting and checking to make sure everything is wired properly. These are cheap and a good tool to have around the house.
Step 2: Wiring Diagram
***See the next page for an explanation of how to wire the system to the engine***
For those of you familiar with electronics, every component is arbitrarily wired in series without regard to polarity. The exception is the ignition coil/capacitor combo which is wired in parallel, and then put into series with everything else.
Please forgive the sloppy diagram; I made in paint. I wanted to use a platform that allowed me to use pictorial symbols rather than conventional electronic schematics which not everyone is familiar with.
-The two primary terminals on the ignition coil are shared by multiple components, and therefore will have two wires coming out of each.
-The raised center terminal on the ignition coil feeds the power that goes to the spark plug. This is where the spark plug wire will connect. (For electronics people, it's the positive terminal of the secondary coil. The negative terminal for the secondary coil is shared with the negative terminal for the primary coil)
Step 3: Wiring the System to the Engine 1
The only reason the wiring passes through the engine is to reach the contact breaker system. The contact breaker is simply a switch inside the flywheel that triggers the spark plug to fire at the right moment in the combustion cycle. The engine is not actually producing any power for the ignition system.
First the easy: attaching the negative (black) wire going to the engine. This wire can be attached to any conductive part of the engine assembly. On cars and motorcycles the metal parts of the engine are in electrical contact with each other, which causes them to make up one large electric terminal. This wire should attach to something secure, like a cooling fin, head bolt, crankcase, etc. I prefer to wrap this wire around a bolt and then tighten it. The place you choose should be free of paint and debris, and I recommend sanding it.
Now the harder part: attaching the wire marked red coming out of the engine. This wire has to be directly connected to the contact breaker inside the flywheel.
Here are the steps to gain access:
-Remove the side cover over the flywheel. Depending on your model this may be the left or right cover, and may also be holding back oil. On my honda xr, I removed the left side cover to access the flywheel, and it did not hold back any oil.
-Remove the flywheel.
1- To remove the nut, the flywheel must be locked in place or else it will simply turn. You can lock it in place by using a special tool. Alternatively, you can lock it this way: remove the spark plug and feed wire or rope down into the cylinder. Once there is enough material to lock the piston against the head, the flywheel will seize and you can remove the nut. It is a regular right hand threaded nut which loosens counter clockwise. Make sure that you will be able to remove whatever material you fed into the cylinder and won't leave any debris behind.
2-Pull the flywheel off. Even with the nut off it is virtually impossible to slide the flywheel off by hand. Using pry tools is risky, so I recommend using the special universal flywheel tool that I mentioned. The tool actually screws into the hole in the center of the flywheel. It is a LEFT HAND THREAD, so turn it counterclockwise to tighten. Once the tool is firmly attached, simply tighten the bolt down the bore of the tool and it will force the flywheel off.
Step 4: Wiring the System to the Engine 2
Just a warning, if you have a lighting system, it will not work if you remove the stator. You could find a way to wire the lights up to the battery but I won't be explaining that. You could even use a hybrid approach to power the ignition with the battery and the lights with the stator, but once again you would have to figure it out on your own and rewire the stator after disconnecting it from the ignition.
I removed the whole stator just to have it out of the way and make things easier.
With the flywheel off, we've finally gotten to the contact breaker points which is what we need. The second picture is a contact breaker assembly removed from the engine. The third is the contact breaker attached to the engine. Note that your contact breaker points will look something like this. Now for that last wire.
The wire marked red (coming from the engine) in the diagram is going to attach directly to the contact breaker points. There should already be a wire connected to the breaker points right where we need to put the new one. You need to remove that old wire and put the wire for the new system RIGHT WHERE THE OLD ONE WAS. If you don't already have a wire there, look for the annotation to the second picture for that location. (*You need to maximize the picture in order to view the annotations*) It is important that you get this placement correct. There is usually a nut there for you to secure the wire.
If you put this wire in the wrong place on the contact breaker, it will directly contact the first wire and bypass the switching effect of the system. Without the switching effect of the contact breaker, the spark will never fire. Make sure you secure this wire in the right place.
Once correctly connected, you have to feed this last wire out of the engine. Make sure you route it in a way that avoids moving parts. There is usually a hole in the side cover to pass the wire out.
With the wire routed out of the way, put the flywheel back on and replace the side cover.
Step 5: Mounting Everything
-Use hot glue to secure components and wiring where you want it.
-Hot glue from a glue gun is extremely useful and incredibly strong. Clean both mating surfaces with acetone or rubbing alcohol first, then let them fully dry before gluing. I IMPLORE you to take the cleaning step! A tiny bit of dirt will cause this method to fail. Done right though and you will have an incredibly strong bond.
-Rubbing alcohol/acetone can easily remove hardened hot glue if you make a mistake.
-Once everything is confirmed working and wired correctly, put a small amount of solder at every connection. This will prevent wiring from physically coming apart, as well as prevent it from losing electrical contact due to corrosion. Just imagine having something small come apart while using your machine, causing the whole system to fail and having to go through every little piece to find the problem.
On my Honda I glued the components to the front of the frame. I glued the toggle switch near the original kill switch on the handlebars and wove the wires back down to the other elements. The most difficult piece to mount was the battery. I hot glued the battery to a piece of wood, then screwed the wood to the front fender up through the bottom. The battery is actually quite secure in this arrangement.
Congrats! If you have made it to this point you should be ready to rock and roll with your new, high power ignition system. Make sure you turn the switch off while not running or else the battery will drain.
Step 6: Troubleshooting
In general the way you do this is to attach each of the leads to the wires in series with circuit you are testing. The battery should be detached from the system, so the wires leading up to it make convenient test points.
A reading of 1 on the display indicates a broken, or "open" circuit. Any resistance value displayed means the circuit is continuous or "closed". On this particular circuit, the resistance should be somewhere around 5 ohms.
If you find that your system is an open circuit, follow this procedure:
While doing this, make sure the toggle switch is in the on position. If this doesn't work, try slowly turning the engine over to ensure the contact breakers are in the closed position. The contact breakers are also a switch, and are controlled by the position of the flywheel. The contact breaker switch will open (turn off) at least once, sometimes twice per combustion cycle.
Once you're sure that both switches are closed, check things piece by piece. For example, put your test leads around just one branch of the system. Start by going from let's say, the battery wire you're using to the resistor. If that registers as an open circuit, your problem lies in that branch. Check to make sure connections are secure, with the wire's insulation completely removed at the contact points. It is possible to have a burnt out component, so check across the terminals of components in a bad branch. (This does not work for the capacitor which SHOULD register as an open circuit across its terminals)
If it registers as continuous, the problem lies elsewhere. Expand the branch. Go from let's say the battery wire to the ignition coil.
The process is then repeated until you find a branch that is an open circuit. Once this is found, you know the problem lies in the most recent addition to the branch and can fix the connection issues.
The second and much less likely cause of a system failure is an issue with the contact breaker. This could be the case if the whole system is getting a good reading from the meter but the spark plug still won't fire. With the meter hooked up to the whole system and giving a closed circuit reading, slowly turn the engine over. Within one full engine cycle the reading must register discontinuous for a brief time when the contact breaker switch opens. The opening of the contact breaker switch triggers the spark plug to fire during the normal engine cycle. If the reading fails to register a discontinuity and some point during the cycle, there is a problem with the contact breaker points. This can be a result of wiring the contact breaker assembly in the wrong place, or a mechanical issue with the contact breaker points.
Lastly, a short circuit could cause the failure of the system. Electricity will always take the easiest path, so if given a chance to bypass elements through a better conductor, it will. Look for places where foreign conducting materials might be resting against the terminals of various components. This includes the frame: if terminals or uninsulated wiring is in contact with the frame they will short circuit.
Step 7: Charging the Battery
1. Purchase a charger designed for charging 12 volt batteries. This is the easiest and fastest method, but expect to spend $30 minimum to buy a unit, and size wise they range from a shoebox to a suitcase.
2. Use your car. Wire the battery to be charged to the car battery, positive to positive, negative to negative, as shown in the diagram. Assuming the battery you're charging is a much lower capacity than the car battery, it shouldn't cause the car battery to drain to a harmful level. The next time you run the car, the alternator will fully recharge the car's battery and replenish the power you took.
If you are concerned about draining the car's battery too far while doing this, you can run the car during the process, in which case the alternator will be the power source of the charge. Assuming you're like me and don't want to run the car just to charge a battery, you could even tuck the battery somewhere under the hood, cables hooked up, and just leave it there as you drive about your normal business. Again in this case, the alternator will be providing the charge, not the car's battery.
3. Build a charger (simple). For this method you will need the power transformer from an appliance you don't need anymore. (Big ass plug, small wire, connector on the end, see the picture) I have a stockpile of these things from old electronics that are long since gone. You can purchase them online, from thrift shops, or any used electronics store. These things are cheap, less than 5 bucks a pop. Make sure it's rated for around 15 Watts of power.
I just learned that smaller "12" volt lead acid batteries actually have a slightly higher output voltage than car batteries due to a variation in construction. I believe they actually output at least 13 Volts. This means that the numbers in the paragraph below are incorrect for smaller lead acid batteries. This problem arose when my 13.8 volt power transformer was struggling to produce the required charge current of about 1.0 Amps--it was producing a mere 0.03 Amps. I don't know the safe range of charging voltages for this particular construction of battery so it will require some further testing, but certainly higher than the previous range. If you have any input on this, please put it in the comments.
I've found that a charger producing 15 volts is enough to charge the battery in a reasonable amount of time. I don't know if this voltage is high enough to overcharge the battery if left charging indefinitely. As mentioned before the guides for regular 12 volt batteries don't quite apply because the smaller ones are of a different construction that produce 13-14 volts, so I have no reference range for charger voltages. If you're worried about overcharging, you can unplug the charger after several hours. Most of the charging is done near the beginning anyway. Alternatively, to check the status you can put an ammeter (multimeter) in series with the charger. When the amperage drops significantly from the initial reading it's time to disconnect. Make sure the meter is in the 10 Amp or similar range. This setting often requires moving a lead to a different port. I'm using a universal laptop charger with the end prepared the same way as described for the wall chargers. 15 volts and up is unusual for regular wall chargers, so you might have to drop 10 bucks on a laptop charger. In a few weeks I will be consolidating this page and removing obsolete material.
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Once you have the transformer, cut the connector at the end off. Strip back the insulation far enough to put alligator clips on. Once you have the clips on, you'll need to figure out which lead is positive and negative. Using the voltmeter function of your multimeter in the proper voltage range, attach the leads of the meter to the alligator clips on your power source. The voltage readout should be whatever you're using, but we're concerned about the sign here.
If the reading's sign is positive, then the leads on the charger directly correspond to the meter's test leads that they are attached to. (The alligator clip attached to the red (positive) test lead is positive, and the clip attached to the black (negative) test lead is negative)
If the reading is negative, then the charger leads are opposite from the test leads they are attached to.
MAKE SURE that the test leads on your mulimeter are set up correctly! If you have them plugged in wrong places, the results will be wrong!
Be sure to label which charger lead is which or you will be doing this again!
To charge your battery with this charger, clip the charger's positive clip to the positive terminal, and negative to negative. This method may take awhile, but the price is right.
In my example, I used a 13.8 V transformer I found in my basement.