kai .. it should spin free and be notchy when the piston is at the top dead centre this is called pinch and its how we measure its compression.

how old is the engine?
how many litres of fuel have you put through it?
do the bearings feel notchy when you turn the crank slowly?

it could be a case of bad o rings in the carb? if so i have spare novarossi carbs from the updated 353 series engines you could try