I don't think it will be the seals, or it would be easy to start when hot, but hard to start cold. What does the left cylinder spark plug show?
Sounds like a fuel problem. One thing to check is the air vent for the carb float chamber (it has the plastic pipe attached to it, next to the drain screw): if that is blocked then fuel cannot get into the main & needle jets. Try using a bicycle pump to blow through the hose, or drop the floatbowl and poke wire very gently through it. Good luck