Points

From MopedWiki

A contact breaker (aka points) is a type of electrical switch, and the term typically refers to the switching device found under the flywheel of the ignition systems of spark-ignition internal combustion engines.

Points, contact points, breaker points, and ignition points all refer to the same part of the ignition system.

How Points Work

What is a set of points? or What are points? Simply put, a set of points is an on/off switch -- a very special on on/off switch.

This "switch" is spring loaded and usually closed. It is opened by a lobe or bulge (cam) that spins around and rubs a block. That opens the contacts about .015 inch (check your manual for exact measurements) and then the spring closes them soon after. Electricity from your coils under the flywheel goes through the points and then to your coil. The coil converts the 6 or 12 volts into high voltage stuff and sends it to your spark plug. Each time the crankshaft revolves, the points open and close and send that voltage on.

On this Honda Express NC50 you can see where the gap should be measured, (the lightning bolt) how the wires connect and a place for adjusting them (star) where the rubbing block touches the crankshaft (right arrow) and the top mounting screw (at the top of the triangle).

The purpose of the contact breaker is to interrupt the current flowing in the primary circuit of the ignition coil. When this occurs, the collapsing current induces a high voltage in the secondary winding of the coil, which has very many more turns. This causes a very large voltage to appear at the coil output for a short period – enough to arc across the electrodes of a spark plug.

Timing

Sounds simple enough, right? The engine may be spinning at 4,000 RPM or more. That’s a lot of opening and closing. In a one hour ride, we expect these to operate 240,000 times. They also have to open and close at the right time. The spark must hit shortly before the piston reaches top dead center. That give the fuel/air mixture a bit of time to start ignition and to produce its power on the way down. This is called timing. If the timing is off, the plug can fire while the intake port is still open and blow smoke through the air filter. You won’t be likely to start it. If the timing is way off. the engine may start but run in reverse. Because timing is set differently on different mopeds, this topic will not be addressed here.

Common Problems

If your points look like this, they need cleaning or replacing

Points cause trouble in many ways. They get old and worn. They can get oily or wet. Oil and water can conduct electricity where it is not needed and cause loss of power. The wires going to them shake and break. The wires may rub against the inside of the flywheel and ground out. Mounting screws can vibrate loose (rarely) and the block no longer rubs against the cam. The spring can break and the points won’t close. Screws or clips holding the wire to the points can disconnect. Running without a cover over their flywheel can be hazardous because one splash of water can stop the moped.

To make the trouble worse, points are under the flywheel. To clean or adjust the points, you need to be peering in a tiny space (often through holes in the flywheel itself) with a flashlight, a feeler gauge, and maybe two screwdrivers. A lift or a table can hold a ped high enough to make the height better, but many people don’t have that luxury.

Many times, problems with the points are accompanied by problems with the condenser. Consider replacing the condenser when you replace your points. (You're in there anyway ... why not?)

Read Fred's Guide for an explanation of how to clean your points.

Replacing Points

So, how do you replace points?

Measuring the point gap with a feeler gauge
(step 10)

1. First, you have to take off the flywheel.
2. Disconnect the wires (keeping track of which ones go where).
3. Unscrew the screw(s) holding the base of the points in place.
4. Install the new points, but don’t tighten up the mounting screws. Add the wires to it and nudge the points over to the crankshaft.
5. Turn the engine by hand (aren’t you glad you pulled out the spark plug?) Make sure you are turning it the same direction it runs.
6. As you are slowly turning that engine, you can see the cam on the crankshaft start to push the points away. You want the farthest place that the cam will push to be resting against the rubbing block. Gently push the assembly into the cam until the points open.
7. Now grab your feeler gauge and get ready to put it in the gap.
8. Slightly tighten the assembly mount.
9. Open the points by hand and rest the feeler gauge between the round contacts
10. With one hand you can use a screwdriver in the notch in the points to move the mounting plate to exactly where you want it. With your other hand, drag the .015 (or your spec.) blade through the contacts, moving the first hand until there is barely a drag on the feeler gauge. With your third hand, tighten down the mounting plate.
11. Check your timing. Cover everything up.
12. Put your spark plug back in, put away your tools and ride.

Brand-specific Info

If the information for a specific brand deviates from the information above, check here for brand-specific information.

Honda Express

• Flywheel removal: Here is where Honda owners are happy folk. The flywheel is bolted to crankshaft. With simple tools it can be taken off to easily expose the points.
• In step #5, when turning the engine on an Express with a tap starter by hand, it is very important to turn it the correct way. You can have serious trouble if you turn them the wrong way.

Garelli

This is what the inside of a Garelli flywheel looks like.

• Garelli mopeds are a little bit trickier. Garellis have the cam for the points inside the flywheel so they can’t be set until the flywheel is in place. On step #10, the adjustment must be done with the flywheel in place working through the grooves.

Motobecane

• Motobecanes have a cam that is a separate piece that is mounted on the crankshaft. It must be in the right place or you will be in serious trouble.

Thanks to 50plus for contributing the first edition of this article and pictures to complement it.