Flamethrower exhaust attempt #1

Looks like you have it set tp only throw flames with the engine off when the exhaust coil is activated... Have you tried wiring it so one position is engine coil on, the next, engine coil off, and the third both coils on? I'm pretty sure the spark could pick light up some of the unburned fuel that goes out the exhaust when at full throttle. You may even be able to get a good flame with it running by switching to a carb that has a fuel enrichener instead of a choke plate to give it extra startup fuel, but also richen up the mix really good for flame shooting... The CNS carb would work great for that trick since it has the enrichener instead of the choke plate and a remote cable choke control too, you could hit the choke then the switch to fire both coils while going at full throttle and it should work. The CNS carb is basically a Yamaha PW80 carb clone so there are tons of them on ebay for around $20 so you don't need to pay almost twice as much for a CNS carb kit.

Actually... there are several motorcycle carbs with accelerator pumps installed... I got 2 Harleys in my garage and they both have pumps on their carbs... Look for some small 4 stroke 50 to 80cc motorcycle carbs on ebay and other places since some of them will have them, most 2 smokers won't have accelerator pumps... Also, any carb that uses a fuel enrichener circuit will run you nice and rich when you pull the choke lever... What this does is instead of having a regualr choke plate, it's actually another fuel circuit, but it only dumps in extra fuel and it doesn't care about throttle position, rpm, or engine load...
And my last idea to feed your engine a lot of extra fuel is installing a power jet, this circuit *normally* taps into your float bowl and the venturi effect sucks extra fuel thru an external jet into the carb inlet right before the throttle slide. look up "mikuni power jet" on ebay and you'll see what I'm talking about, By teeing off your fuel line and using a shutoff valve, you can run the extra fuel anytime you want and shut it off when not needed so the engine isn't constantly flooded by an over rich mixture when not in use. I'm sure if you really want to get creative with a power jet, you could run a copper capillary tube to carry the fuel to the tailpipe, you could even run a capillary tube thru your muffler to heat up the fuel, or just simply wrap it around the pipe a few times so it injects a fine mist into the exhaust stream, then when you fire the rear plug it'll throw flame as far as the exhaust gases can be shot out your tailpipe.... No fuel injection or pump needed...

My friend's bike, fatdaddy, http://m.youtube.com/watch?v=FSPC9Vo6hmY

We think the combination of a shorty pipe, old burnt out honeycomb baffle, and slightly rich carb cause the fire breathing