Electrical DIY FAQ - Read This Second

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OK... so after reading the Electrical 101 post, you should now have a basic understanding of the theory behind the electrics on your motorcycle.

The next question on most people's mind is how do I do X, Y, Z?

Well, have no fear! This thread will attempt to answer some of the more basic and frequent questions in plain English.

For the purposes of this thread, questions and answers will be kept to a novice-to-intermediate level and I've locked this thread to keep it free of clutter. This thread will be most useful if all the information about a given topic can be found in a single post and not require multiple pages of reading.

Please feel free to PM me with any additions or amendments and I will incorporate them into the thread.
Re: Electrical DIY - Read This Second

Can I use a Lithium Ion Battery?

Yes, but probably not without changes to your charging system. Lithium Ion batteries are sensitive to how they are charged. Exceeding 14.5V will cause damage over time and exceeding 15V is likely to cause damage in a very short period. It's not uncommon to see 16V at high RPMs on some of our older bikes. The voltage regulators of the day just weren't as effective as today's options.

Luckily, you can buy a modern regulator (often in combination with a rectifier) to fix this problem.

If you are unsure as to whether or not your charging system will suffice, warm up your bike and then put a multimeter across the battery terminals. Rev the bike up to near redline (again, only do this on a warm engine) and check voltages. If you don't exceed 14.5V you should be OK.
Re: Electrical DIY - Read This Second

How do I remove electrical component X from my bike?

Removing a single item, such as a horn, from your bike is fairly easy and straight forward. 90% of the time it's as simple as unplugging it and calling it good.

It's always a good idea to have an understanding of what's happening, however. Not all items can be simply removed without causing further complications.

The first step in this process will be to have a wiring diagram to which you can refer. If the item you're looking to remove in a series circuit then you need only remove the item and continue the wiring run. There is one caveat though, if it's the only item in the wiring run (e.g. the neutral light on a Honda) then you want to remove the wiring run as well. If you were to remove the light and continue the run, you would blow a fuse every time you shifted into neutral. See the attached pic. The section outlined in red is what would need to be removed for a successful "deletion". Whenever possible, remove all the wiring along with whatever you're taking off. Loose wires are confusing and unnecessary.


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Re: Electrical DIY - Read This Second

How do I do an LED conversion?

LED conversions are usually pretty simple. Many manufacturers produce LED bulbs in standard sizes and nine times out of ten these can just slot right in with no changes. LED headlights are starting to become a little more commonplace and entire tail light sections can now be seen in LED formats.

Generally speaking, most of the problems in an LED conversion will center around the turn signals.

In all of our old bikes the signal relay depends upon a certain level of current in order to create the flashing you see when you signal left or right. Because LEDs use so little current, this isn't enough to trigger the flashing in the old relay and so the lights will stay solid.

There are two solutions to this problem. The first solution is to add resistors to each of the lights, but this is a poor option. Part of the reason for going to LEDs is to use less power and if you add resistors to the circuit, you're using more power. The true solution to this problem is to replace the stock turn signal relay with a digital model specifically designed for LEDs. These can be had for under $10 and it's a lot easier than wiring in a bunch of resistors.

Another common issue, especially with Hondas, is that the stock indicator light (in the dash) isn't setup to handle LEDs. This is because LEDs are polarized. Current will only flow through an LED in one direction. That is, the positive and negative matter. Incandescent bulbs don't care about polarity and the Honda engineers used this to their advantage to simplify the wiring. If you want to keep the indicator light but also use LED turn signals, some changes will need to be made.

For a stock indicator light, both the left turn signal wire and the right turn signal wire connect to the bulb and the wires alternate as the positive and negative depending on which direction you're signalling. For LED signals, this indicator light now represents a crossover that will cause all four signals to light up at once, regardless of which direction you're signalling. The solution to this problem is to the polarize the indicator light by preventing current from traveling between left and right circuits.

This is done by treating the left and right signal wires, together, as positive and then adding a ground wire into the circuit. The current can be "forced" in one direction by the addition of an electronic component called a diode. A pack of three can be had from Radio Shack for about $2.

By removing the left and right signal lights from the indicator bulb and wiring a diode onto each end, we allow the current to flow into the bulb, but not back up the other side's turn signal circuit. After the diodes, the two circuits can be spliced together and we now have no worries about the crossover. The spliced section (shown in black on the attached picture) acts as the indicator light's positive side and the negative side gets a new ground wire that you will need to attach.


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Re: Electrical DIY - Read This Second

I want to simplify my wiring. What electrical components can be removed from my bike?

This is a tricky question because nearly everything can be taken off the bike. The legalities are your main concern, along with how much use your bike will be on the street.

Racing bikes often run what is called a "total loss" ignition system. This means the only electrics on the bike are a battery and an ignition system. All of the lights, gauges, and even the charging system is removed. When the battery is dead, so is the bike.

To make this a bit more roadworthy, you can add the charging system back into the mix, but it still is unlikely to be legal.

Think about what is necessary for your DMV inspection and what you're willing to live with or without and that's the answer to this question.

As far as simplifying the wiring, that can take many forms. Ignition switches can be replaced or bypassed with cleaner options. Wiring runs can be shortened, hidden, and/or cleaned up (I often ditch most of the ground wires and use the frame, instead). The sky is pretty much the limit and your components won't care as long as they're getting the power they need. Design it first, then execute it.
What Ohm Rating Should My Resistor Be?
As mentioned in the Electrical 101 post, there is a definite relation between current, voltage, and resistance. What this means in the real world is that you can run lower voltage items on a higher voltage circuit by adding in resistors.

It's possible to run some of your old 6V electronics after upgrading to a 12V charging system, for instance. You can also run a 3V LED.

To make this possible, you need to know how much voltage is required by the component you're wanting to install. Let's use the 3V LED as an example.

Assuming we're on a 12V system, this means we have to account for an additional 9 volts of electricity.

Next, we need to measure the resistance across our component to calculate its current usage. You should recall that I = V / R and we know that our LED is operating at 3V, so this equation should now read I = 3 / R. We measure R out to be 1500 Ohms and completing the rest of the equation lets us know that we're drawing .002 amps.

So we now know that our resistor is operating at 9V and .002A. Ohm's Law gives us a resistance value of 4500 Ohms. Also, by multiplying the resistor's voltage and the circuit's current, we know that the resistor needs to be able to handle at least .018 Watts. 1/4W is a standard size for resistors and this will be fine. So by utilizing a 4500 Ohm rated at 1/4 W we can run a single LED on our 12V system.

What if you want to run two LEDs? Simply recalculate. Double the current and reduce the resistor's voltage by 3. 1500 Ohms will work for this one.
How do I know which battery is correct for my bike

After deciding whether or not you can use a Lithium Ion battery (see above post), the next thing to look at is the different types of batteries available.

Batteries can be found in the following flavors:
  • Flooded Cell Lead Acid - This is the style that was generally available when most of our bikes were made and 99% of the time, this is the stock battery type. The only advantage of this type of battery over the other types is that this type is the most resistant to overcharging. Too much voltage and too much current will not damage this battery type except in extreme cases.
  • Sealed Lead Acid - This style is not dissimilar to the flooded cell, except that they are sealed to prevent spillage. This makes them "maintenance-free" so that you do not have to top up the electrolytes, but it also leaves them less capable at dealing with excess voltage and current. These can be mounted on their side, but not upside down. Try to mount them vertically if you're able, however. These are generally the cheapest batteries available and can be found in battery backup supplies in alarm systems and computer components. These types of batteries are also known as VRLA, or Valve-Regulated Lead Acid.
  • AGM - AGM stands for Absorbed Glass Mat and these types use very little electrolyte. These types of batteries are the most commonly used in automotive applications. They can generally be mounted upright or on their side without any difficulty. They are maintenance free and perform quite well for deep-cycle application (where current is required over long periods). Shallow cycle versions are also available (where a large amount of current is needed, but only for a short period). AGM batteries are the current yardstick and perform adequately for most applications with few negative traits.
  • LI-ION - Lithium Ion is the new comer to the automotive battery world. They're expensive and fault intolerant, but they are insanely light and small and can be mounted just about anywhere. LI-ION batteries do not care for a lot of vibrations, they hate overcharging, and they'll probably catch fire if there is any internal electronic failures. Furthermore, any voltage above 14.5V will significantly shorten their lifespan (voltages can exceed 16V on stock charging systems). That said, a lot of folks will use them just because they're cool (yes, I want one, too).

So... maybe you have an idea of what type of battery you want, it's time to investigate the specs for each individual battery. Voltage aside, there will be two numbers which will be of importance.

The primary concern is the battery's Amp Hour rating (usually abbreviated as Ah). This number is an approximation of how many hours your battery will be capable of discharging it's rated voltage at one amp. So a 9 Ah battery should be able to continuously discharge current at a single amp for nine hours.

Your service manual will specify a minimum number for batteries that go into your bike. You can go smaller, but to do so risks draining the battery even under normal operation of the bike. If your bike has seen some improvements to the alternator, reduction in wattage requirements (LED lights, low-wattage headlights, removal of non-critical electrical systems, etc) you can usually get away with a lower rating.

Your riding habits will also affect your Ah requirements. If you spend a lot of time riding in the city (or otherwise idling the bike) you may not want to drop to anything much smaller. Also, if you spend all your time are redline and haven't upgraded to a modern regulator, you may not want to go with anything smaller (Ah rating is also a battery's resistance to overcharging). If you're cruising on the highway all day every day, you can cut your Ah way down because the battery will be facing very little discharge and won't have to cope with too much overcharge, either.

So, why go smaller on the Ah rating? Well, the Ah rating correlates to the size and weight of the battery. Smaller batteries will generally have lower Ah ratings.

The second rating you will usually find is Cold Cranking Amps (also listed as CCA). This maximum current your battery can provide for a continuous period of 30 seconds at 0°F which maintaining a voltage of at least 7.2V. In reality, this number will indicate how well your battery can turn over your starter motor. This number isn't always listed because it correlates closely to the Ah rating of the battery in most cases. Marine Cranking Amps (MCA) is also sometimes listed and this is the same requirement as CCA, except the battery is measured at 32°F instead of 0°F. Obviously, if your bike doesn't use a starter motor, this rating isn't of much importance to you.
Can I get rid of my battery and use a "battery eliminator"?

Well... if your bike uses an electromagnetic alternator then, "No".

But if your bike is running with a permanent magnet alternator then the answer is, "Probably not".

I'll be talking about the Honda twins from the 60's and 70's, but this applies to all permanent magnet alternator bike.

The problem with the Honda twins is that they don't produce enough wattage to run all that's needed. They came that way from the factory. Break even point comes in at 3000 or 4000 RPM depending on the strength of your charging system.

If you really want to ditch the battery and go with a battery eliminator (which is basically a large capacitor), you need to reduce the amount of power your bike uses and/or increase the power output of the charging system.

The first is much easier, but the second is also worth considering.

To reduce the wattage requirements, your best bet is to pull as many lights as possible. LED replacements are also an option assuming you need/want to keep some of the lights. Access to electronic ignitions that can decrease your dwell also work, as does higher resistance coils. I advocate the change to a new regulator/rectifier as well, but some units will not decrease your wattage consumption; choose carefully. All wires should be examined and cleaned of corrosion and dirt.

To increase your power production, you have a few choices. Most common is to pick up an aftermarket stator such as the one available from Rick's Motorsport. Many alternator specialist shops can also rewind your existing stator (more coils in the stator means more power) as an upgrade. If you wanna get a little crazier, you can try something like this: http://www.dotheton.com/forum/index.php?topic=38872.msg500741#msg500741

After each change, you should test to see if you've hit your goal. This is simply done by hooking up a multimeter to your battery with the bike turned off and with the battery sitting (without being charged or having the bike run) for 24 hours. Your reading should be somewhere around 12.5V. Now start the bike with the kick starter are let the bike idle until warm; about five minutes or so. Measure again. If you're at 13V or better, pull the battery and stick an eliminator in there; you're good to go.
How do I read a wiring diagram?

It is said that a picture is worth a thousand words. In the case of wiring diagrams, this is definitely true.

Wiring diagrams are an effort to put down on paper how the wiring is routed within your motorcycle's electrical systems. A good diagram will include all of the electrical components (including switching and sometimes even the connectors) and all of the wiring runs.

Each of the wiring runs is done in a different color wire in order to make it easier to trace the flow of electricity, and each of the major motorcycle manufacturers will often use the same color wire for the same circuit across many models of bikes. This last part is important to remember, because if you know what a certain color of wire is for on a CB125, you can have a pretty good idea of its purpose on a CB350.

As mentioned in the Electrical 101 post, current flows from the positive terminal of the battery and back to the negative terminal. This flow of current must be completely uninterrupted or no electrical work is being done. It's not enough to hook up a light to the positive or negative terminal alone; it only works when you have a complete circuit. In order to prevent circuits from being complete, we add mechanical devices called switches into the circuit. Turn the switch off to break the circuit and stop the flow of electricity or turn the switch on to complete the circuit and allow the electricity to flow.

So how does this apply to reading a wiring diagram? Well, in order to make the best use of a diagram, it's important to first identify the wires that are carrying current to a component from the positive battery terminal and then the wires that are carrying current away from the component and back to the negative terminal. Then we can also identify any switches that are used to control this current flow.

To begin, take a look at the negative terminal of the battery in your diagram. There will usually be a thick black wire coming from it and going to ground, but there will also be a colored wire joining in at the terminal. In the case of the attached diagrams (and for Hondas as a rule), this is a green wire. 99% of green wires on a Honda will be a ground wire. As mentioned above, all electrical components need a connection to ground or they won't function. So we know that everything we want to run needs to eventually connect to either the frame of the bike or to a green wire.

Next, eye up the positive terminal of the battery. This one is a bit more complicated as we usually have several connections here. You'll see wires running to the rectifier, starter motor, and the ignition switch. Ignore the first two for now and focus on the switch. We know that switches are used to control the flow of current and when they're off, so are our components. So what happens when we turn it on? Where is the current going now? Looking at the switch's schematic, we can see that in position one, we're bridging the gap between the red and black wires. With the ignition switch on, the black wire now has current. Continue tracing the black wire and you see see it feeds most of the electrical systems on the bike. This black wire is known as the "switched hot" wire. It can be thought of as the "trunk" from which all the individual circuits will branch.

By now, you've probably noticed a couple of other diagrams attached to this post. Aside from the "official" diagram, I've also attached a diagram I put into the Simplified Wiring Diagrams post and then one I've made just for this post. The two diagrams I've made are functionally equivalent (with the exception of the omission of the neutral and turn signal indicator lights aka idiot lights), but they're drawn in different manners to help illustrate the concepts.

The difference between the official diagram and the original simplified diagram are as follows:
*Removal of the horn
*Gauge backlights and running lights are on from the ignition switch, not the headlight switch
*Combination regulator/rectifier replaces separate stock units
*Connections from coils to points are implied and are not shown in my diagram
*Removal of electric starter, solenoid, and wiring to the starter button
*No high beam light
*Ground wires are implied for all components

The differences between my original diagram and the one we're using for teaching purposes are these:
*No idiot lights shown at all (so no wiring for neutral or indicator lights)
*All ground wires shown
*Some slight differences in wiring colors

So with those differences in mind... lets follow the wires on the simplified diagram...

Tracing back from the negative terminal of the battery we can see all the components have a ground. Perfect.

Now tracing forward from the positive terminal we can see that when we get to the ignition switch, the wire colors change from red to black (wire colors will almost always change at the junction to a switch). The black wires past the ignition switch are switched hot. Following the black wire we can see that it feeds the tail light, the speedo and tach backlights, the flasher relay, the kill switch, both the brake switches, and the high/low switch.

Each of these switches then controls the flow of electricity to an electrical component. Because each component has it's own switch, individual (parallel) circuits can be controlled without affecting other systems.

Try a few mental exercises and see if you can figure out what changes to make for the following modifications:
*Add a single switch that controls the headlight whether the high beam is on or not
*Remove the kill switch so that the coils will have power so long as the ignition switch is on
*Remove the front brake switch so that the brake light still works if the rear brake is pressed
*The the turn signal indicator light back into the circuit
*Run a secondary fuse for the headlight circuit
*Add the starter motor, solenoid, and starter switch back into the circuit without affecting the operations of the other devices
*Add an AC relay that controls power to the headlight such that the headlight will not turn on until after the engine is running

Hopefully, that's enough information to get you started. If you run into anything or have any questions, go ahead and PM me and I'll help as I am able.


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Can I use my two dual-filament bulbs as turn signals as well as running and brake lights?

Yes. Yes, you can.

Many bikes from the late '70s and on came equipped with two bulbs in the rear cowl. Each of these bulbs would function as both a brake light and a running light because of their dual-filament nature.

If you're to ditch your rear turn signals you can make use of this stock configuration to ensure your bike remains safe and legal. It looks pretty cool, too.

You'll need a few spade connectors (or relay sockets) as well as two four-pin relays. These usually run six or seven dollars at most auto parts stores. Make sure to buy the generic universal parts because dedicated relays can approach $30 each. You may also need some wire, heat shrink, crimpers, solding iron and other assorted electric tools (depending on how you want to make the joins into the existing harness). Also needed will be a 10W resistor. You usually aren't able to pick these up at Radio Shack, so look online. They're big and ceramic coated.

In the attached picture, I've used Honda colors, but it should still be fairly evident what's going on.

The brown wires are carrying current as soon as the bike is turned on, so the relays are getting power as well as the running lights. When the brakes are pressed, current flows through from the 85 pin to the 86 pin on the left and from the 86 pin to the 85 pin on the right. If you're using LED turn signals, this may end up lighting the front signals, and so the use of diodes is recommended. The 85/85 pins on the relay energize the circuit and complete the connection between pins 30 and 87. So now we have power flowing to both filaments on the bulb. Likewise, when either turn signal is activated, just that specific relay is energized as the current will flow through the relay, to ground, through the resistor we added on the brake lines. It's important to note that relays are not polarized, so they can be activated when current flows in either direction. As the turn signal flashes, so does the brake light on that side.

Or, if you're not feeling in a DIY mood, go pick up one of these:


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How do I test if my ignition coils are good?

In order to test if your ignition coils are working, there are several multimeter tests one can perform, but often it's a lot easier to just perform a bench test.

To test a coil on the bench, you will need three wires (preferably with alligator clips) and a charged battery (in the same voltage as your coil).

First, place your ignition coil on the bench with the spark plug wire, cap, and spark plug all attached properly to the ignition coil.

Next, take one of the wires and connect the threaded portion of the spark plug to the negative terminal of the battery.

After that, connect the negative terminal of the ignition coil to one of the wires, but leave the other end of the test wire unconnected (for the moment).

Finally, connect the positive terminal of the ignition coil to the positive terminal of the battery.

At this point, you should have almost everything you need. With a close eye on your spark plug gap, touch the wire coming off the negative terminal of the ignition coil (the one that has been left unconnected up to this point) to the negative terminal of the battery and the pull it off of the negative terminal of the battery. When the wire is disconnected, a spark should be visible from the coil.

This spark should be white or blue in color. If the spark is yellow, orange, or even red, your battery or your coil (most likely your coil) is on its way out. It may also be worth checking your spark plug wires, spark plug, or plug cap if these are replaceable items on your coil.
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