You could probably tap in a switch so when you hit the kill switch a plug in the exhaust would spark and then engine would throw gas into exhaust.
Would maybe want to put a switch before that wire.
Like run two CDI's, I believe kill switch just cuts one wire to CDI, so if you ran two, but when you push the kill switch it grounds to the 2nd. Then add a swithc so your not always throwing flames when killing the engine, unless thats desired.
No idea if that'd work, you also need oxygen in the pipes for a good flame.