What it likely is, is just the fact that it's a new, tight engine. It's not all that uncommon a problem.
Here's what you do;
First, pull the glow plug and drop 1 or 2 drops of after-run-oil in. Then put the glow plug back in, snug it down and then back it off about 1 turn. Now take a hair dryer or heat gun and heat the engine up until it's very hot to the touch. While the engine is hot plug the exhaust and pull the pullstart until fuel just reaches the carb (not going into the carb - just till fuel reaches it). Now conect the glow plug and try to start the engine.
After you get through about 3 or 4 tanks of fuel the engine will have losened up enough that you won't need to preheat it anymore.