rotax 399cc no spark

[classic-indy]

I was trying to get spark on my 1972 rotax 399, but no such luck. Thought it was fouled plugs, so i put a volt meter on the plug from the magneto to the coils??? we had voltage, so I checked at the spark plug cap and still had voltage.

So i thought it must be the spark plugs, replaced them with the correct plugs and still no spark. I was pressing the plugs against the engine to ground it.

What could be wrong?

 

[jakecrank99]

Just because you have voltage at the plug cap don't mean you will have spark. There might not be enough voltage to jump the gap and give you a spark. You need to check for to much resistance of the plug wires (1000 ohm per foot is standard). Other things could be corrosion at connections, week coils, or if it has set for a long time a rusted fly wheel and internal coils.