Question about point gap

[eavega]

So, in replacing all the ignition components in my FD-22, I have become curious about something; why is the point gap so specific? If the points are just there to close a circuit and transfer a charge into the spark plugs, what does it matter if the point gap is .020" or .030", or for that matter .5", as long as the points close at the correct moment.

-Eric

 

[rickdb1boat]

Re: Question about point gap

The amount of gap determines ignition timing. The wrong gap will result in the timing being either advanced or retarded too much..

 

[tashasdaddy]

Re: Question about point gap

the gaps also give the coils the time to "charge" to send appropriate electricity to the plug. if it is off, the motor will not run correctly. the point gap is ,020. the spark plug gap is .030.

 

[F_R]

Re: Question about point gap

As the flywheel magnets pass the first two legs of the coil's laminations, and start past the second two, the polarity of the generated voltage in the primary winding reverses. The points have to open at the exact correct time in relation to that reversal. The gap is related to the time that they open because the rubbing block contacts the cam slope sooner (or later) according to the gap. It is the reversal that causes a high voltage to be induced in the secondary winding. The condenser also figures in that reversal, but you didn't ask about that.

 

[jay_merrill]

Re: Question about point gap

As the flywheel magnets pass the first two legs of the coil's laminations ....

This is a great post! I love to understand exactly what is going on with a motor or component because I feel that helps me to troubleshoot a problem.

Thanks FR!

 

[ThumbPkr]

Re: Question about point gap

Also the inductive (coil) and capacitive (condensor) reactance are calculated to arrive at the total impedance of the circuit and if the values are not adhered to pretty closely the performance suffers and the points tend to transfer material from one contact to the other which reduces point life.Ron G

 

[lambertfam]

Re: Question about point gap

So if the gap wasn't set correctly, how would that make the engine run? Would it still run or would it backfire and cut out? Could this cause misfires in one cylinder or even cause one cylinder to not work and therefore cause a lack of RPM at the prop?

 

[tx1961whaler]

Re: Question about point gap

A wrong point gap will cause an engine to run crappy or not at all.