make, model and year of the bike? Is the carb brand new out-of-the-box or only 'new' to you?
Did the bike ever idle with this carb? How about with the old carb?
Run without the filter and see if it idles.. if it still doesn't idle, the filter has nothing to do with this problem. Maybe some sediment has already gotten into the carb and clogged the idle system.
I'm not a big fan of additional filters.. they are just something else that can get clogged up or spring a leak.. the guys who built these bikes put enough filters and screens on them .. as long as the fuel system is kept clean the bike should run fine.