Compression+spark+fuel=running engine. All the other things mentioned
above will just mean it'll run badly.
Easiest way to isolate problem (assuming there's compression and the previous owner hasn't done something daft like fitting cam belt incorrectly)
is to remove the hose leading to the throttle butterfly + get a mate to spray some 'easystart' into the inlet whilst you turn it over.
Easy start is like an enviromental disaster in a can and will start ANY
engine. If it runs then dies when you stop spraying it's a fuel problem
(You have checked there's fuel in it not just relied on your fuel gauge)
if it doesn't fire it's igniton.
Hope this helps good luck.

P.S.
If it is Ben's, the guy to speak to is Jamie at Jamsport cos he's recently fiited a whole new management system to it, which if it is an ignition problem
might make sense.