oil blowing out of muffler

No air box. It has been removed separate filters on carbs . where the crankcase breather is there is a 90 degree pipe that is open so don't think back pressure is the problem but i'm open to anything.

well going to try the valve guide replacement . can some body let me know are the intake and exhaust the same size The sites i visited with sets all 8 look alike but if you look at oem #s slightly different , maybe inside dim is different. Any help would be great. Thanks
 

Well it's crow eating time . well i did replace the valve guides on #2 cylinder they had a little play . and still blowing oil . I stripped it back to the pistons and actually took out the rings to inspect them. even though they were new i found a default in the oil ring . One of the upward tabs were missing allowing that side to slide under the other .when i was checking as per Nessism's post it was hard to see and you could move them apart making me think it was ok ,So even though they were new i now know to look more closely  and make sure parts are good  So thanks Nessism you were right . Bike runs great