If the new spark plugs don't help ... I would definitely send the ignition module to DA for a check.

I had the same problem at the end of last season ... hard to start ... had to use an electric starter.
The problem seemed intermittent ... changed plugs etc. as you are doing.
Finally the engine just quit in flight at the bottom of a loop. Sent the whole engine back to DA ... they found a bad ignition module.

I was on my third ignition module after only three gallons of gas. The original module did not work right out of the box.

On the bright side ... now that I have six gallons of gas thru it, it starts runs and idles fine. I had the stall problem before I had used five gallons of gas.


Good luck !