OK, I was lazy and only did schematic here and I haven’t tested this but I think it should work.
Timing_light_new.fzz (12.4 KB)
I swiped the 555 circuit for a monostable from here (which also has the calculations for the r2/c3 values to set the monostable time which you will need to figure out):
https://www.electronics-tutorials.ws/waveforms/555_timer.html
The monostable triggers on a negative edge so you may need to invert the leads on L1 so that the leading edge of the spark pulse is going towards ground to get it to trigger correctly. I’d replace the 1n4001 diodes with 1n4148 switching diodes which are faster than the 4001s. They are there to keep the input voltage in to the 555 between ground and +12V to not blow the 555. Hopefully the current coil produces enough voltage (it will need about -8 volts to trigger I think, increasing the value of R3 may help if it won’t trigger as is). What this circuit does is stretch the input pulse width to being longer than the trigger, so you need to figure out what the maximum frequency of the input pulses will be at top revs and adjust the monostable pulse width to be about half of that. In theory that should get you more light (as the led is on a bit longer) and as a bonus should eliminate the second pulse if the monostable is set to stay on longer than the second trigger pulse when the spark goes off (assuming that is what is causing the two strobes which seems likely). You can replace R2 with a pot so you can set an approximate C3 value and vary the time with the pot to set the time experimentally. The ideal way to do this would be to have an oscilloscope where you can see the input waveform at the trigger on pin 2 of the 555 and the output from pin 3 on the 555 while doing the adjustments. As well this circuit will switch the MOSFET gate between 0 and 12V (so you need to make sure the mosfet has a max gate source voltage higher than 12V) but most any MOSFET should be driveable with this you don’t need a logic level mosfet as now. The drawing in the tutorial article shows how the output pulse is longer than the input trigger much better than I can explain in words 
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Peter