Well, if you have spark and you introduce fuel directly into the intake, bypassing the fuel management, it should fire. Unless you have no compression or a vac leak. Simple rule. Fuel, spark, compression and air, but not too much air and the engine will run. Maybe you should run a comp test. For something like this you need to start with the basics before guessing and throwing any parts at it. These 103s are pretty simple engines....Are you sure you're getting nice blue spark? Can you hear a nice tapping spark if you hold the plug suppressor just off the tip of the plug while cranking. Are you checking your spark at the plugs or at the coil? This has got to be something very simple. Check to see if your bridge at the end of the cam is broken to see if the rotor is spinning. they do break sometimes and will have spark off the coil, but it won't
make it to the plugs.........I'm really curious now..