In The CBX Ignition, Parts 1 and 2, we looked in detail at the pulsers and spark units, including how to test them. Now we’ll take a close look at the ignition coils.

Hummm, zzzaaap!
Most people know that an ignition coil is actually a transformer. It steps up the battery’s 12 volts to a potential of thousands of volts. We’ve learned so far in these articles that ignition coils do their work in short bursts initiated by the pulsers and switched by the spark units. Like a transformer, the ignition coil is made of two windings. As explained in Parts 1 and 2, the coil is saturated first, then turned off, resulting in the collapsing of the magnetic field in one of the coil’s windings leading to the rapid build up of voltage in the other. Other than the substitution of pulsers and transistors for the age-old points, all of which are merely signaling and switching parts, there is nothing here that is different from the old Kettering ignition that powered that old Honda 350 twin you had back in high school. It’s a pretty ancient design. 1907, remember? I know, I keep emphasizing this. But it’s useful to keep in mind because it prepares us to look for some of the same problems as are found in the classic Kettering system, and it helps us know how to tackle them.

High performance ignition coils
High performance ignition coils for the CBX are much in evidence these days, even more than when these bikes were new. High performance coils are very simply just coils whose windings are differently proportioned than the stock coils. That is, the winding’s turn ratios are different. This difference in turn ratio results in a higher potential voltage output. But remember, no coil fires at its voltage rating, but rather at the precise voltage that will bridge the spark plug gap under a given load. What’s the point of high voltage coils, then? Really, the starting and torque benefits are pretty theoretical. But improved carburetion isn't. Huh? Yes. More efficient combustion makes less a demand on fueling, resulting in the carbs going from barely supplying the needed fuel to actually providing surplus, due to more efficient combustion. "Hot" coils in effect richen carburetion.

Maintenance and testing
Probably the most high-maintenance part of the CBX ignition system is the plug wires. However, the reason for this need for maintenance is not what many think, that the wires are like automotive plug wires and need replacing every so often. Hondas never need their spark plug wires replaced. Unlike car wires, they are permanent, stainless steel wire that never breaks down. However, like car wires, their terminals can corrode and get loose. So check them. Remove the plug caps and resistance test them. They should be no higher resistance than 5K ohms. Also make sure the caps are screwed onto the wires tightly, and the wires to the coils. And, look for signs of arcing from the wires to the frame.

After looking for the obvious things, then go on to component testing. However, don’t get in a dither about how to tell which of the three major parts in your CBX’s ignition system is not working correctly. It’s easy. In Part 1, we looked at testing the ignition pulser. All you need is an analog multimeter. Part 2 showed us that the best way to test the spark unit is to test around it. If you have no spark, and after visually checking the system and then testing the pulser and ignition coil they test good, the spark unit is the problem. The ignition coil is perhaps the easiest of the three to test. Remember, all the ignition coil does is turn on with the keyswitch, then turn off at a pulse signal, and the spark plug fires. To test the coil, first check for battery voltage at the black/white wire, with the keyswitch and kill switch turned on. If that’s good, then disconnect the colored wires from each of the three coils (blue, yellow, and pink) and simply jump a wire from the battery’s negative terminal to the exposed terminal on the coil being tested. Disconnect and reconnect the jumper at the coil intermittently. Each time the jumper is touched to the coil and then removed, the spark plug should spark. This test simulates what the spark unit does, by grounding the negative side of the ignition coil. Pretty simple, eh? Forget the official manual’s coil resistance test – it’s not conclusive enough.