Here’s a question almost as provacative as what brand of 2-stroke oil is best…..

[amuller]

I do ad FrankR says. If the points are installed, or accessed through a window in the flywheel I fold a strip of paper over a popsicle stick, or piece of saw blade, or whatever. But I like to take the point set apart and dress the contacts separately.

[mike-stroz]

I usually just use a points file and feeler gauge set I inherited from my grandfather. It was good enough for him for 50 years so it’s good enough for me. If I’ve done them in the past and they’re just a little dirty I just use some fine grit sandpaper for a couple swipes and some isopropyl alcohol to get them clean

[rudderless]

…just so ya know..
..contact points scrub sideways during the engagement and disengagement process to keep them clean..or to scrub away any oxide that developed during their operation. A contact that sticks closed is worn and has craters that keeps the contacts from moving sideways which holds them closed when they are supposed to open. This scrub is about oxide management.

Contact points for motors do not scrub sideways. They need a high pressure contact area for oxide management…which is why one point is convex. If both points are flat and touch evenly the oxide that forms between the points can form a film of insulating oxide and can keep them from touching or contacting. The oxide can return much sooner on flat contacts with no scrub since there is no hi pressure area to push or beat through the oxide.

Point is if the points are worn flat they should be properly reshaped if one doesn’t want to be back under the wheel any time soon.

So…new motor runs great for years. Out of nowhere the spark stops after years of use. One cleans the points of the oxide and spark returns…for a little while. So the point system gets a bad rep for high maintenance when actually they need reshaping or replacing to reestablish their reliability.

[rudderless]

So lets add a capacitor to the points…usually on a DC circuit. To keep the spark from welding the points together one can use a cap across the points. As the points start to open the potential of one contact will fall and an arc will form jumping between the points. A capacitor will discharge into the lower potential contact keeping the potential equivalent until enough space opens up between the contacts to prevent arcing. When the cap is fully discharged the circuit is open.

On a spark system the cap keeps the charge in the coil from leaking back out through the arc of the points, loosing coil energy. The points open, cap keeps the coil charged until enough space develops between the points. When the cap is discharged the mag flux collapses into the secondary coil causing the plug to spark. If too much cap..the arc will move material to one contact…if too little the other contact will gain material.

..ya didn’t ask about this but..

[Monte NZ]

Thanks Rudderless and all
Very interesting…….we never know it all and .now I am a bit wiser!

Monte NZ

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