You were correct about the spark quitting when it gets hot.
The wire seems OK. Would you suspect the coil or switch or what?
Is it worth while to replace coil or switch?
I don't see the type.
It's a Poulan Woodsman 2150.
Eng. Family: TPWO42ub24RA:EM
Eng. Disp. 36cc
The part number isNNN-NN-NNNNand can be purchased from a Poulan dealer or http://www.searspartsdirect.com/ see link 2150