Dirtbike ignition system: power consumption

I am trying to calculate the amount of power that a Honda CRF450 dirtbike's ignition system (ignition coil + spark plug) will consume. I'm not very familiar with ignition systems and the currents they involve - what is the easiest way to calculate this?

So far, I've found that the ignition coil's resistance is 0.1 - 0.3 $\Omega$, so the power (while charging the coil) is $$P_{active} = \frac{V^2}{R} = \frac{(12~V)^2}{0.1 \text{ to } 0.3~\Omega} = 480~\text{to}~1440~W$$ Then, if I pick an engine speed of 5000 RPM as an example, the time between sparks is $$T = \frac{2\text{ revs/spark}}{(5000~\text{RPM}) / (60~\text{s}/\text{min})} = 24~\text{ms}$$ If I estimate the dwell time as 2 ms, then the average power consumption is $$P_{avg} = \frac{2~\text{ms}}{24~\text{ms}} (480~W \text{ to } 1440~W) = 40~\text{to}~120~W$$ This is a huge range, and the higher end of the range sounds too large. Is there a more precise way to estimate this average power?

• such a range should not pose a problem, consider the energy output of the engine over the same speed range. – Jasen Nov 8 '15 at 1:03
• @Jasen: I've picked one specific engine speed (5000 RPM), where I know my engine's power output. – Greg d'Eon Nov 8 '15 at 1:13