Hi!
Agree with Gene!
It sounds as if you just run the engine too lean....
Too high temperature will make the engine hard to start (cylinder have expanded away from the piston wich reduces compression ).
Some advise.
Before each flight ..hold up the nose of the airplane and set the needle somewhat rich from max rpm....hold it upp for 5-15 seconds...dont shake the airplane... Just hold it still with the nose pointing upwards.....rpm should be stable!

Jan K