I really like the name [name_u]Harley[/name_u] for my third son but it seems to be really popular for girls from what I can find online. [name_f]Do[/name_f] you think it’s too girly? My other sons are [name_m]Kiefer[/name_m] and [name_u]Van[/name_u]. I love [name_u]Harley[/name_u] [name_m]Koda[/name_m].
[name_u]Harley[/name_u] isn’t a girly name but it is used more on girls than boys so that’s something to think about! I like it though and think it works well with your other boys names 
I like [name_m]Koda[/name_m]! But I think [name_u]Harley[/name_u] is more associated with girls now, since [name_u]Harley[/name_u] [name_u]Quinn[/name_u] or however you spell it. [name_f]Harlow[/name_f] might be another option for you. That is also a unisex name, but I think it’s more true unisex. You could even spell it Harlo to make it seem more masculine. But it’s up to your tastes! I personally would not use [name_u]Harley[/name_u] for a boy. Depends on how much that majority feminine association would bother you.
I know many many boys named [name_u]Harley[/name_u] and only 1 girl. Sounds very boyish to me, it must depend on where you live.
My thoughts were [name_u]Harley[/name_u] > Motorbike > Boy.
The only [name_u]Harley[/name_u] I’ve ever known was a guy, so I think you’re fine. Like @spoonfulofsugar mentioned, it makes me think of [name_u]Harley[/name_u] [name_m]Davidson[/name_m] which is a rather masculine brand.
I disagree that [name_f]Harlow[/name_f] is more unisex, as a pp poster mentioned. There isn’t even data on here for it as a boy’s name, so not terribly unisex. I definitely think [name_u]Harley[/name_u] is more unisex. It ranks within the top 1000 for both genders, even if it is more common for girls right now. I wouldn’t let that bother you though. People are usurping perfectly good masculine names for girls. It’s a thing right now. Doesn’t make most of the names sound less masculine in my opinion.
[name_u]Harley[/name_u] is 100% masculine to me. Never met one of either gender but I also associate it with the motorcycle brand. I think [name_f]Harlow[/name_f] is more feminine than [name_u]Harley[/name_u].
[name_u]Harley[/name_u] has more a unisex vibe for me that either of your other sons’ names. I don’t think it has the same masculine feel as [name_m]Kiefer[/name_m] and [name_u]Van[/name_u]. I think [name_m]Harvey[/name_m] would go better with them.