You must realize that by doing this, you have no filtering at all on the power leads from the receiver to the CDI, right? The Opto you have may as well not even be there, because you are piping the CDInoise directly past it on the power leads. Luckily, you can often timesget away with this on a 2.4 gHz radio, but you should also be aware that you now have a greaty diminished safety margin in the event that something else goes wrong. For example, suppose the plug cap comes loose, but does not completely detach. The noise now coming back along the wiring has just gone way up.

Also, please be aware that it does not necessarily require 2.4 gHz energy to interefere with a 2.4 gHz receiver. Every spread spectrum receiver has a frequency synthesiser curcuit in it that is fed by a fixed frequency crystal controlled oscillator, most likely one running at 10 mHz. So, if you bring enough RFnoise into close enough proximity to the synthesiser circuitry, bad things may happen. And the fact that you have now effectvely turned your receiver power bus into a broadcast antenna for CDI noise isn't such a good idea. You may get away with this, but you should at least consider going to a separate ignition battery if you don't want to usea device that would filter the power leads. Good luck!