With the cylinder and bottom end soaked in fuel, it doesn't always work out that well. The plug is only a small part, with a lot of fuel in the engine..
I was taught to light it on fire. Both plug and whole. Watch out you will possibly singe some hair on the back of your hand. Lol but works like a charm.
You could just pull the engine over several times with the plug out and it helps.... But the fuel is still everywhere. Normally a lot of bogging and smoking upon start up.
I tried the decomp valve, but it seemed to make it worse. After following advice, from this group, I did 1 pull with the choke followed by 2 pulls without and it fired right up. I noticed that the chain was really tight from the store, so before I got to revving it, I took the bar and chain off completely (just to do it) and made sure the tension was right when I put it back on. I will have to do some cleaning this weekend, but all in all it looked pretty good on the insides, as well. After messing with the bar and chain, it started right up, first pull. Oiler seems to be feeding great, but I will have to adjust the carb, sightly. There was a previous comment, on another thread, that since it was a rental saw the adjustment screws may be epoxied, but everything is accessible on this one! Noodled a round like it was nothing. So glad I got this saw. Looking forward to some actual cutting soon.
It was some of the older 6400's that came with the epoxied h screw. The newer saws like you have there are all fully adjustable now.
I was taught the lighter trick too by an old logger, after he flooded my MM'd 660 (compression north of 200, no decomp or elastostart). But I flooded it really bad one time, and it didn't work. WOT method always works.