Hello!

I am restoring a Fairmont RK-B engine (2 piston , 2 strokes), both sparkplugs should fire at the same time, i am using this circuit :http://tinyurl.com/yacjj8fc (falstad/circuit), it works fine for another Fairmont engine we have (1 piston, 2 strokes). I tried connecting another coil in parallel to the ignition coil , both coils produce spark , but it's not strong enough.

Do you have any advices?

 

Your circuit doesn't make sense... Usually the points and capacitor are in parallel on the ground path of the coil.

 

Ideally you use a dual output coil (two outputs, not one) or two single coils in series.

I have a old Fairbanks Morse 2 cylinder generator that works that way. If both coils are in parallel (As I acquired it) they have weak spark and burn the points out after a few hours of run time.
But once I put in series they both had good spark and never gave any further points issue either although ideally it should have had a single coil with dual outputs rather than two single coils.

As for the schematic you link to I too have no idea what they are going for being a properly designed points and condensor based ignition system only needs a single capacitor/condenser in parallel to the points. Adding more and too much capacitance elsewhere on the points side of the coil just make things worse.

 

So your wanting two plugs to fire at once? You didn't mention the primary voltage needed. If 6V, an old style Harley coil has two spark plug leads that fire at the same time. 12V gets you many more options, a 12V harley coil or even one coil off of a GM 'coil pack' from the 1980's

http://www.jpcycles.com/product/380-086

https://www.ebay.com/i/231747712166?chn=ps&dispItem=1

https://www.summitracing.com/search...iac/engine-size/3-8l-231/coil-style/coil-pack

 

Thank you very much for your advise, i connected the coils like this http://tinyurl.com/y9ampnzk (falstad/circuit) and finally both coils produced a decen t spark (i think), it was a bench test. I will try to start the engine tomorrow using that circuit.