1975? T500 wont idle

[Jakeyz333]

Hey guys I bought a supposed 72 t500 until I did a little research and found it seemed to be at 75. Either way I bought it for 225 dollars n he told me all it needed was a battery.... Boy was he wrong. A year into it my neighbor who owns a bike shop and I couldn't figure out what it was so I got fed up and took it to a local shop. So 3 months and 2200 dollars later k get it back. The dude rides it around the lot I was kind of in a hurry so I paid him and got along. When I finally got home it started right up...when to let it idle and it just puttered out..after looking they had put the idle all the way in on the carbs and it Still wouldn't idle...it'd scream if you jus kept the rpm up manually. But its really bad in low end they said the compression was low and the crank seal on the right side might be going out. But I didn't have the money to replace it so I just brought it home. Idk if its that reason its not idiling I'm not sure. I don't have the airbox cover ATM either. So if anyone has any suggestions on what could be the issue please let me know. Much appreciated -Jacob