Many of the models introduced before the late 70's using mechanical contact breakers (commonly known as points) to control the ignition signal. There are various reasons for malfunctions in the ignition system, but we should start by checking the condition of the points and the functions around the points before worrying about ignition timing. If the problems are improved, not only the idling will be stable, but the acceleration performance will be smooth and pleasant. Now, let's challenge!
- Check the ignition of the spark plug.
- Be careful not to loosen the plug cap screw-in.
- Just a point, but it's still points!
- To clean contact stains, pull out a piece of paper between them.
- Degreasing contacts. Why do we need oil felts?
- Inner rotor type AC generator
- The moment you pass the "F" mark, the point opens.
Check the ignition of the spark plug.
If the spark plug does not produce a strong spark, the engine condition will not be pleasant. If you suspect an electrical problem, especially when idling is unstable, try pressing the threaded part of the spark plug against the cylinder head, turning the key ON, and cranking the kick pedal with an empty hand. If you can't get a strong spark even though you press the plug firmly, or if you get a chattering electric leak on your hand, you should recheck the condition of the ignition coil area.
Be careful not to loosen the plug cap screw-in.
When checking the condition of the ignition coil area, remove the plug cap from the high tension cord (unscrew it), cut the end of the cord with nippers by about 5 mm, and then screw the plug cap back on. At the connection point between the plug cap and the cord core wire, there is a wood screw on the plug cap side, which bites into the coated core wire to connect the wires. You can also apply a small amount of power feed grease (grease with copper powder) to the cut end of the cord so that it can be screwed in smoothly.
Just a point, but it's still points!
The Super Cub 90 and MD90 of the old engine era used a battery ignition system, and the points=contact breaker is laid out inside the camshaft end cover. Before removing the points base, mark the base plate and the tightening head area (mark the points base so that it can be easily recovered). For ignition control, does the spark advance device (also known as the governor), which varies with engine speed, work correctly? Pinch the point cam and try to rotate it. If the point cam moves smoothly while pulling the spring, it is correct, but if it is stuck or moves unsteadily without moderation, remove the advanced device, disassemble and clean it, and investigate the cause of malfunction and repair it.
To clean contact stains, pull out a piece of paper between them.
Once you have confirmed that the spark advance panther is working, restore it to its original state and clean the dirt from the point contacts. To do this, step on the kick slowly to the crank angle where the points are closed, and when the points are closed (when the point heel goes from riding up the camshaft mountain to the base circle), put a folded piece of copy paper between the point contacts and pull it out quickly. By doing so, you can easily remove the dirt from the point contact point, and you can also see how dirty it was.
Degreasing contacts. Why do we need oil felts?
After cleaning the point contacts, lightly rinse the dirty parts with parts cleaner, dry them, and soak the oil felt with grease to reduce wear on the point heels and camshaft mounts. Point-controlled models always have a point camshaft, and the oil felt is responsible for constantly supplying grease to eliminate sliding resistance between the camshaft heel and the point heel. If this felt has been removed or is missing, be sure to install it. Also, if it is dirty and dry, loosen the clumps and soak up the grease.
Inner rotor type AC generator
The old Cub 90 has a magnetic inner rotor specification instead of an outer rotor. Since the points of the outer rotor specification are hidden behind the rotor, the outer rotor must be removed using a special tool when performing the work practiced so far.
The moment you pass the "F" mark, the point opens.
The default ignition timing can be achieved by adjusting the points so that they open at the moment the rotating F mark passes the engraved line that serves as the alignment mark. For a typical 4-stroke engine, the ignition timing is approximately 10 to 12 degrees before top dead center at idling, and 30 to 35 degrees before top dead center after ignition advance. After ignition, the angle of advance is 30 to 35 degrees before top dead center. In the case of high-tuned engines and racing engines, the angle of advance is even higher. Incidentally, the Honda CR110 racing engine, a 4-stroke racing 50cc twin camshaft engine, has a fixed advance angle setting of 55 degrees before top dead center without a governor. This should give you an idea of how high RPM the engine is.
- Point 1: When the idling of a point model is unstable, check the plugs, carburetors, and points in that order to get an idea of what to look for.
- Point 2: Poor operation of the spark advancer (governor) is a cause of poor engine start-up.
- Point 3: If you can understand the principle that spark plugs fly sparks at the moment the points are opened, ignition system maintenance will be fun.
In the case of battery ignition models, the generator and points (contact breaker) functions are often laid out separately, while in the case of flywheel magnet ignition models, the points are often laid out in the outer flywheel. In the case of the moped class or single-cylinder engines with large displacement, the latter type of flywheel magnet ignition system motorcycles seem to be more common. When the parts are laid out separately, it is easy to see the moment the "F" mark (fire mark), which indicates the ignition timing, passes the timing tick line. In the case of a vehicle with a flywheel magnet ignition where the points are laid out on the inside of the rotor (flywheel), visually check the moment the points open by looking through the confirmation hole on the side of the rotor. At the same time, while moving the rotor, adjust the points so that they open at the moment when they pass the timing tick line on the outer circumference.
If you are a veteran mechanic, you probably have a lot of experience in adjusting these points, but it is really a tough job to get them just right for the F mark. Although not used in this photo, a timing light (also known as an ignition light or ignition strobe) is a great tool to have when adjusting the ignition timing. This is a special tool that allows you to set the clip of the timing light on the high tension cord while the engine is running (to align the marks as the electricity flows) and then strobe the timing inscriptions to make it easier to align the F-marks. If the rotor's F-mark is engraved earlier than the fixed engraving line, the point base can be moved to adjust the timing. If the points are located on the inside of the flywheel, you can stop the engine, adjust the point gap slightly, start the engine again, and check again to match the F-marks.
Unlike today's engines where the ignition timing is set perfectly as long as the parts are assembled exactly as specified, the engine of an old points type engine will not be in good condition if the timing is not correct. There is a saying that maintaining the condition of an old motorcycle starts with controlling the electricity, and it is important to own a timing light in order to control the electricity.
