Quick question re: spark

[mrlmd]

Just checking - In setting up a tach, like the Tiny Tach or any others - does the fe290 engine produce 1 spark per revolution or 1 spark every 2 revolutions, ie., only on the power stroke?

[Spicyunicorn]

I believe it's one spark per revolution so spark on compression stroke and exaust stroke someone will correct me if I'm wrong

[wicked872]

the 4 stroke engine only fires on the top of the compression stroke so every other revolution.

[Cartmaster]

Most small engines run a wasted spark system to simplify the ignition set up. So my assumption is that it probably fires once per revolution. you should be able to try it both ways and see what results are closer to the engines specification. I dont know the fe290 engine well, so cant confirm my thoughts but i am sure someone on here will know.

I believe that the standard top speed of the fe290 is around 3600 rpm so if the tack says double this or half this at WOT then you have it set wrong LOL.

Edit.

Looking at the spec of the engine it is a simple flywheel ignition system, so almost certainly wasted spark, so one spark per rev. This type of system is also used on some small twin cylinder engines with twin coils but a single igniter like on the ezgo robin twins. Simple but very effective.

[mrlmd]

I thought this was a wasted spark ignition system, ie., a spark on every rev of the engine because of simplicity and weight savings - just wanted to check.

Wicked872 - that applies to larger, more complicated engines, but many small single cylinder gas engines, like in lawn mowers, motorcycles, scooters, mopeds, chainsaws, and golfcarts, etc., have a spark generated every revolution and are called wasted spark ignitions.