Mark,

A couple of things to consider. First, DAs need to be "hand propped" more briskly than some other engines or electronic ignitions that use Hall Effect switches.

Secondly, it is possible that the reed valves are not closing as well as they once were causing fuel draw to be reduced. My DA 50 exhibited some of the same symptoms but after modifying my starting procedures I am satisfied now. One the first start of the day; insure the choke is fully closed and flip the prop aggressively until it pops(may take many more flips if you drain the fuel after each flying session) or runs for a bit. Open choke and flip until it starts. If it then dies, close choke and start over. Good luck.