1990 Kx80 Clutch

bike had a bad clutch replaced it changed oil to a thicker weight now when i start the bike and drop into gear it stalls unless im on the gas like the clutch isnt engaging all the way. figured out when its fulled pulled it grabs but let out of the clutch a little it stays like in neutral then releases like it should. it has power and seems to be there on everything but the top end. was wondering if anyone had any advise on what the problem could be. or how to diagnose easier or better explain let me know.

basket plates and the pack the plates sit in aswell. top end hasnt been done sense ive had the bike. its also a bitch to start.. been wanting to compression test it.. havnt gotten around to it. bike seemed to run fine before just fell on its face with the clutch slipping.. new bike to me so it could just be ballless. my buddy rides a rm250 everyday and he said that it felt like it had no top end but he also said he is used to bigger bikes.