A question for engine experts (Russ, etc)

[newrider3]

So, I was sitting around tonight, playing with a Briggs Quantum 5hp shortblock, thinking of stuff to do with it. While turning the flywheel, and observing the magnet position at TDC before the power stroke, I also noticed that the magnet is there at TDC just after the exhaust stroke. Does this mean that there is a second spark occurring, but an inert one due to the fact there wouldn't be any air/fuel in the cylinder? Or is this negated within the Briggs Magnetron electronic ignition set-up? Just something I had never thought about before, and thinking one of you guys would know better than me.

 

[modelengineer]

It's wasted spark ignition, there is nothing combustible in the cylinder so it doesn't do anything.

 

[devino246]

I had though about that too, but figured the spark was wasted like modelengineer said.

 

[Russ2251]

This is usually the source of backfire after a misfire meaning a weak plug.

 

[DirtTrackRacer_07]

If your motor was over jetted and did not burn the fuel completely and you had a open exhaust, it would give off a nice back pop on deacceleration.

But if it ignited on the exhaust even a little it would help clean the combition chamber out a little more.

 

[Thedude]

there is one spark per rotation