It could be a worn needle in which case a stronger spring will help. Possible debris on top of the diaphragm also...sawdust loves to hide there. Also as mentioned earlier check the needle arm height... it should be the same height as the carb case with a straightedge. If that is correct you may want to excitement at this point.... adjust the arm so there is a slight air gap and try. This will lean the fuel delivery out just slightly. This has worked for me many times with a saw prone to flooding and Dolmars are easy to flood. Each saw is a little different which most setting still work, occasionally a saw is slightly different and needs set slightly different.
Best way to start a flooded Dolmar:
1. Engage chain break
2. If you have a log with a kerf or bore put bar int it to help stabilize.
3. Make sure choke is open. Then hold throttle wide open.
4. Pull like crazy...when it starts it will be 4 stoking bad and a lot of blue smoke... pull saw out of cut, release the chainbreak and run it until it cleans up and acts normal.
I use this procedure when I have a carb I've modded and takes a different tune than normal...they will flood until it's found or I find an issue.