Honda auto choke

Bought a new mower which starts ok from a cold engine and a warm one providing I start it within about 5 minutes of stopping it after use. If I leave it longer it will not start. I have checked the choke plate and found it to be closed, l have then pushed it open , held it in this position and it starts first time. I can only think that the choke plate is closing too fast and because the engine is still warm it will not start. The dealer has replaced the wax cylinder which appeared to be stuck in with silicone but he did not replace this when a new one was installed. The new wax cylinder did not cure the problem . Does the silicone make a difference? Can any one please advise. Thanks John