Yes, I see. Karp-os, I'm troubled a bit, though -- so I studied it some more....
It seems the KJV translators see no real distinction, using "fruit" and "fruits" (See Romans 8:23) in spite of the Greek.
Roman 8:23 And not only they, but ourselves also, which have the first fruits of the Spirit,...
Actually, they do. See text analysis of Romans 8:23 here
http://biblos.com/romans/8-23.htm
firsfruits in greek is aparchēn not karpos
Original Word: ἀπαρχή, ῆς, ἡ
Part of Speech: Noun, Feminine
Transliteration: aparché
Short Definition: the first-fruits
Definition: the first-fruits, the earliest crop of the year, hence also met., for example, of the earliest converts in a district; there is evidence in favor of rendering in some passages merely by: sacrifice, gift.
8 occurrences in the NT
Romans 8:23 N-AFS
BIB: αὐτοὶ τὴν ἀπαρχὴν τοῦ πνεύματος
NAS: having the first fruits of the Spirit,
KJV: which have the
firstfruits of the Spirit,
INT: ourselves the first-fruit of the Spirit
Romans 11:16 N-NFS
BIB: δὲ ἡ ἀπαρχὴ ἁγία καὶ
NAS: If the first piece [of dough] is holy,
KJV: if the
firstfruit [be] holy,
INT: moreover the first-fruit [be] holy also
Romans 16:5 N-NFS
BIB: ὅς ἐστιν ἀπαρχὴ τῆς Ἀσίας
NAS: who is the first convert to Christ
KJV: who is the
firstfruits of Achaia unto
INT: who is a first-fruit of Achaia
1 Corinthians 15:20 N-NFS
BIB: ἐκ νεκρῶν ἀπαρχὴ τῶν κεκοιμημένων
NAS: from the dead, the first fruits of those
KJV: [and] become the
firstfruits of them that slept.
INT: from among [the] dead first-fruit of those fallen asleep
1 Corinthians 15:23 N-NFS
BIB: ἰδίῳ τάγματι ἀπαρχὴ Χριστός ἔπειτα
NAS: Christ the first fruits, after
KJV: Christ the
firstfruits; afterward
INT: own order [the] first-fruit Christ then
1 Corinthians 16:15 N-NFS
BIB: ὅτι ἐστὶν ἀπαρχὴ τῆς Ἀχαίας
NAS: of Stephanas, that they were the first fruits of Achaia,
KJV: it is the
firstfruits of Achaia,
INT: that it is first-fruit of Achaia
James 1:18 N-AFS
BIB: εἶναι ἡμᾶς ἀπαρχήν τινα τῶν
NAS: that we would be a kind of first fruits among His creatures.
KJV: a kind of
firstfruits of his
INT: to be us first-fruits a sort of
Revelation 14:4 N-NFS
BIB: τῶν ἀνθρώπων ἀπαρχὴ τῷ θεῷ
NAS: men as first fruits to God
KJV: among men, [being] the
firstfruits unto God
INT: the men [as] firstfruits to God