Help wanted on a 2012 arctic cat wildcat 1000

Help!!! Okay where to start hoping to get some advice since this  is my first arctic cat wildcat 1000 with that being said I bought a 2012 arctic cat wildcat 1000 awhile ago and I had the the whole motor rebuilt everything is brand new beside the transmission and clutch and some sensors  one problem I have is it’s hard to get in gear like you almost have to feel like your going to break the gear shifter putting it in gear but you can kind of rock back-and-forth with someone putting it in gear and it goes right in that way what could cause this ? Brand new shift cable as well 2nd it runs kinda funny I think wanted to get someone’s opinion on if that’s how they are supposed to sound like and it will run for couple a mins and die every time just when it’s idling other then that it runs  great and no problems no engine codes or lights on if that helps and when you first start it every time it runs like I think it should sound then start running funny I think only at  idle any advice would help or if it supposed to sound like that