I can tell just from looking at your pictures that your valve spring
IS NOT tight enough
You have tightened the stop nut that holds the valve spring bolt all the way, but the bolt itself is still set too loose. I sent you a pm, but you can just follow the steps in the link in my sig below, or in this pic:
After you loosen the stop nut, you need to stick the allen screw into the top of the valve spring bolt and tighten that by turning clockwise. Once you get it tight enough that when you rev it doesn't stall, then you tighten down the stop nut again to prevent the setting from changing.
When you are all done, you should have no more than 7 (probably less) threads of the valve spring bolt visable above the stop nut.