best thing I can tell you is to check the manual and set the low and high needles to the factory locations and try it there. If you still have issues, replace the glow plug.
Getting fuel to the carburetor my glow plug igniter does not work all the time and when I started it have to put down on a glow igniter Conflict for about 5 to 6 minutes but never no smoke
The higher the nitro methane content, the more power you will create, but you will also create more heat and shorten the life of the engine. If you want it to last, use the 15%.