Is this the RTR or the SS? I don't know much about the 15fe engine, but my 12R SS is exceptionally easy to start. However, I also let it idle (exactly like the directions say) through the first 6 tanks, and I destroyed a piston and sleeve. I no longer idle engines at all during break-in, not enough heat. In any case, mine was hard to start and hard to keep running once it got warm after it lost all compression. New piston and sleeve, broken in at 200 F for 6 tanks, then standard break-in after that and it runs great.

You said "loose metal sound" and thats NEVER good. Pull the ehad and backplate and see if there is any sort of debris inside the combustion chamber or the crankcase. That could very well explain why you broke the pull-start. The only other reason would be a flooded engine, but a flooded engine doesn't make "loose metal" sounds.