Hard to start

[6xchevy]

My 50 3100 has the original 216 which if I start her up a couple times a week does fine but if she sits for a couple of weeks takes forever to start up. A little gas or starter fluid in the carb does no good. Compression cold is 105-115 psi, points in good condition and gap is set to factory specs, spark plugs and coil has been replaced. The 6 volt battery actually spins the crank good. Any thoughts on why she is so hard to start? Thanks!