Umm...Nick ? put down the chainsaw......heh....try that #66 Jet - with a 15mm Carb and a #82, it's probably gargling on the fuel instead of firing it.
Spin the plug out and use a hair dryer on it, if it's wet when you pull it.
If you get fire with the #66, check the mix asap...and make sure that's not too lean, given that you have 50:1 in the tanks.
Always try lean first...it's easier to fire, and then richen up to a good point, rather than the reverse...it saves a lotta headaches of this sort.