When you talk to the experienced riders who enjoy tinkering with old motorcycle. One of the clichés they all say is, "You need to own as many spare parts and repair parts as possible. I guess they are right. In this section, I will report on the repair of an electrical (ignition) problem by removing a spare part from the same engine and installing a used part.
Spare engine worth buying!
I pulled out a Kawasaki air-cooled 90cc single-cylinder engine that I had purchased at a garage sale (parts exchange event) and had pushed to the back of the shed, and said, "I wish I could use it." I checked the rotor and prayed that it would be okay. Half of the inside of the rotor had been submerged in water in the past. There were traces of water on the inside half of the rotor. This was the only spare engine and spare parts I had on hand, but it looked like it would work.
To remove the flywheel, use a special tool
When removing the flywheel (outer rotor), use the rotor holder to stop the rotor from turning, and then loosen the center nut. This anti-rotation tool can be used on various models, so it is a must-have for any Sunmeca. After removing the center nut and washer, use the flywheel puller. The large screw on the flywheel side is a reverse (left) screw, so first tighten it to the bottom of the screw with your fingertips, then push the Jumonji puller in to remove the flywheel.
There are two types of power generation coils, one for ignition and one for charging.
The upper left coil of the three coils, to the left of the points when viewed from the side of the engine, has a coil with thin enameled wire wrapped around it. This coil with many turns of thin wire is the "ignition exciter coil". When it gets hot from continuous running, does it cause an internal short somewhere in the coil? The coils on the right and lower left are "charge coils for recharging," which feature thick enamel wires wound around them.
Day? Night? Wiring replacement by priority!?
I was able to borrow the manufacturer's service manual, and when I checked the electrical circuit and electrical component specifications of the compatible model, I found that it was the type that allows you to switch the amount of charge by replacing the wiring color. The instructions were to switch the wiring between daytime and nighttime driving, and between the most frequent usage. Nowadays, this would not be possible since the headlights are always on, but it seems that the 1960s models had this kind of usage.
Power generation power changes with decreasing magnetic force!!
The specifications of the built-in normal flywheel vary depending on the model, and some models seem to have the magnet cast into the aluminum body. I used a screwdriver shaft to check the magnetic force of the magnet cast inside. We found that the flywheel could not be lifted even with the screwdriver shaft. On the other hand, the flywheel that was removed from the spare engine was obviously very strong and could not be easily removed when the screwdriver shaft was attached to it. I also replaced the points and capacitor with spare parts as part of the maintenance. After reassembling, I went out for a test run and found that there were no symptoms of fire loss as before.
- Point 1: If there are models with the same series of engines, even if they are not the same model, check the compatibility of such engines.
- Point 2: In some cases, special tools can be used across the boundaries of motorcycle manufacturers. Let's check the screw size first.
When I'm just cruising around the neighborhood, nothing happens, but when I go out for a little touring, I hear "ping, ping, ping!!! Suddenly, the motorcycle seemed to catch fire. After a few minutes of resting on the shoulder of the road, the motorcycle returned to normal as if nothing had happened. ...... The cause of the trouble is generally thought to be one of four places. Ignition coil? Points & capacitor? Flywheel? Or ignition generator coil? I started by removing the parts from the spare engine I owned and trying to replace them.
However, when I went out touring, I always had a strange problem with my Kawasaki 90, which seemed to occur when the engine was running at full throttle and overheating. The problem was always the same: when the engine warmed up, the symptoms appeared. The problem is always the same: when the engine gets warm, it starts to "ping, ping, ping.!!After a semi-restoration, the motorcycle returned to the road. Returning to public roads after semi-restoration. Immediately after that, these symptoms occur. At first, I thought, "Could it be the IG coil? So I replaced it with a spare IG coil. However, the same problem occurred again.
I once had a similar symptom on a Honda 4 mini with a 4-stroke engine, a symptom that is caused by a "capacitor failure" connected to the points, as is the case with most 6-volt motorcycles. When the engine is cold, for example, the specified value of the capacitor is 0. Even if it is 25uF (microfarad), the numerical data changes as the engine warm up (0 when measured with a capacitor tester when warm)..(There was a time when it was 85uF.) The capacitor would misfire and stop the engine without being able to function as it should. Or, even if the engine can idle, it will not start up at all. When this symptom occurs, if you look into the point contact while the engine is starting (look into the back of the rotating flywheel), you will see sparks coming out of the point contact while the engine is idling. Similar symptoms occurred in a CDI motorcycle with a 12-volt engine.
I had a CDI motorcycle with a 12-bolt engine that had a similar problem, but it had a special lightweight racing flywheel installed. So, I removed the flywheel cover and let the running air cool it down, and the symptom disappeared.
Based on the above experience, I had an emergency plan in my mind that if I had a problem with poor ignition (loss of fire), "just remove the flywheel cover and let it cool down while driving". However, I still couldn't drive comfortably without troubleshooting the problem. So this time, I removed the coil base assembly from the spare engine and replaced the whole set. I decided to replace the entire base plate of the ignition coil (exciter coil) and the charging coil (charge coil).
The charging circuit seems to be different (the number of rising wires is different), so I rearranged the connection and started the engine. Then, when the engine was idling, it started at 6. The voltage was around 2 volts, and when the engine was revved up, it exceeded 8 volts, so we concluded that the power generation function was fine. We will have to wait until the engine is warmed up to test the exciter coil, but we were able to complete the tour without any problems.
At the touring destination, I visually checked the point contacts while the engine was idling, but there was no spark and it was fine. After that, nothing happened and I was able to enjoy the touring. You never know what will happen to an old motorcycle, but when you are able to shoot the cause of the trouble, it is an irreplaceable feeling of joy.
