The tail light looks good. I am sure that I'm getting spark. It isn't incredibly large and bright, but there is spark there (I recently bought a new spark plug). As far as whether or not the decompression valve is fully closing, it certainly seems like it. I took apart the front coil (where the spark plug attaches) and cleaned it out really well. The valve closes fully. It also doesn't open up very much when the lever is pulled (thoug the spring is fully compressed when I pull the lever).
The break light doesn't appear to be burn't out. Is there any way to test it? With the idle screw, what way should I turn it to begin with? Should I put it in all the way and then adjust it once (and if) the engine is nice and warm?