points operations?

[csisommout]

Can any body explane the operations of points. When is it sopposed to close and open fo 1964 28hp, 2cyl Evinrude. Thank you.

 

[tashasdaddy]

Re: points operations?

the points open and close due to the oblong shape of the crank shaft. the opening allows the coils time to recharge between firing.

http://forums.iboats.com/showthread.php?t=294072

 

[Chris1956]

Re: points operations?

On your motor, when the points open, they cause the magnetic field in the primary coil that was induced by the flywheel magnet, to collapse. This collapse induces a very high voltage spike in the secondary coil winding, firing the plug.

Points are generally set to a particular opening(older J/Es use .020 in) at the "top" of the point lobe. This gives the igniiton system the proper static timing. As engine speed increases, the points need to open sooner, to give the spark time to build and fire. The spark advance is controlled by moving the points in relation to the point lobe.

 

[kbait]

Re: points operations?

Nice Chris!

 

[csisommout]

Re: points operations?

Do both points takes turn to close and open. the reason I ask because whem I turn flywwheel by hand in 1 resolution I only see top cyl point closed.

Never see the other close. thank you.

 

[Rudi2]

Re: points operations?

Do both points takes turn to close and open. the reason I ask because whem I turn flywwheel by hand in 1 resolution I only see top cyl point closed.

Never see the other close. thank you.

Short answer, yes - points "takes turn"

When the cam opens #1 points, voltage rises and coil fires #1 plug. Breakers close, flywheel continues to rotate and duplicates the process for #2 point set to fire #2 plug.

 

[JB]

Re: points operations?

To expand a bit on Rudi's post, there are two seperate magnetos, one for each cylinder. They share the magnets in the flywheel and the cam that operates the points and therefore times the spark.

The point sets are adjusted individually to a clearance of .020" when at max opening.

 

[JSGOLD]

Re: points operations?

"Never see the other close. thank you."

If the one set of points NEVER closes that is a bad thing...they should alternate , open/closed, if stuck open something is worn or points are out of adjustment...Lord, I remember my first car and my mini bikes/motorcycles using points....not used that much anymore on newer stuff. But they did the job!

 

[bktheking]

Re: points operations?

Do both points takes turn to close and open. the reason I ask because whem I turn flywwheel by hand in 1 resolution I only see top cyl point closed.

Never see the other close. thank you.

This is what I thought the problem was in your other post, one set of the points isn't opening, they alternate on a twin cylinder engine. Fix your points and enjoy your motor.

 

[Vic.S]

Re: points operations?

While on the subject of points

On another forum there was a question recently about a '68 55hp 3 cylinder Johnson. It has two sets of points (and a distributor)

Why two?

 

[JSGOLD]

Re: points operations?

I've seen 4 cylinder engines such as car and motorcycle have dual points...in fact the last time I worked with a car with points it had dual ones. Not sure why a 3 cylinder motor would have them...

 

[bktheking]

Re: points operations?

It must be the way the timing is setup and the arrangement of the crankshaft and distributer, the 85 hp 4 cyl has only 2 as well.

 

[F_R]

Re: points operations?

I've seen 4 cylinder engines such as car and motorcycle have dual points...in fact the last time I worked with a car with points it had dual ones. Not sure why a 3 cylinder motor would have them...

It has two sets of points, but a 3-lobed cam. BOTH sets of points are used to fire each of the 3 times per rev. It is to acheive the proper dwell. One set makes the circuit and the other breaks it. This is all in conjunction with the amplified battery CD ignition system.

 

[Vic.S]

Re: points operations?

Thanks for the explanation. That answer was given on the other forum but the person who answered did confess to not being sure about it.