Infinitive clauses referring to an adjective before a noun

We know that infinitive clauses can sometimes refer to adjectives before nouns. I feel with what adjectives they can do that, but I don't have any reason for it.

Examples;

You can buy the best book to read. = You can buy the book which is the best to read.

I have enough money to go to Italy. = I have money that is enough to go to Italy.

I met a nice friend to hang out with. = I met a friend who is nice to hang out with.

Whereas the sentences above are okay, why are the following ones wrong?

(If they are also correct, then there is no problem, but someone said they were wrong. I am not sure.)

I saw the ready machine to run for 10 hours =? I saw the machine which is ready to run for 10 hours.

I met a motivated person to win the competition. =? I met a person who is motivated to win the competition.

I have an eager girlfriend to hang out outside. =? I have a girlfriend who is eager to hang out outside.

Thank you very much in advance.