i have arcade as a companion and he wont talk to me about how he was enclave and that im idolized by the ncr ive done the gomorah quest and mr house wants me to kill the bos ive taken to silver rush repcon hq and the crashed vertibird and im accepted by the followers how do i start the quest?

ive had this exact problem, and its pissing me off! I WANT MY REMNANT POWER ARMOR

All I know is that you have to some of these to gain his trust, check mark the ones you have. You need... like 1/2 of them or so...

-Take him to crashed Vertibird
-Take him to Silver Rush
-Take him to REPCONN
-Complete one of these: A) For the Republic B) Wild Card: Side Bets C) The House Always Wins < required
-Accepted by the F.O.T.A
-Neutral or lower w/Legion
-Choose "Let's get in, see what he's up, and get out" when you enter The Fort
-Head to the Old Nuclear Site Shack

Not in any order of course. OFF TOPIC QUESTION: if I side with Yes Man, will I still be fighting with the NCR at the dam? I am unsure whether to do 'Side Bets' or 'For The Republic'.

There's no reason both of these problems couldn't be covered in your first topic. There's also no reason that they shouldn't have been posted in spoilers.
http://www.gamesas.com/index.php?/topic/1138338-arcade-gannon-quest-help/

You have to reach the point in the game where it says you cannot continue, which means you have to reach pretty much the end. Obviously, choose the option that says you are not ready(or whatever it was).

Try talking to him after you have dealt with the brotherhood

he just talked to me got his fathers armour and some remenant enclave armour with helmet and remenant armour without helmet(from dead prospector)

You can get it without talking to him, you just gotta find it. And trust me, it's one hell of a fight.

Found the helmet that way, I was going for the armour but ran out of armor penetrating ammo halfway through :facepalm: