ms280 won't run with muffler on

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Hello, new to the forum. I work on quite a few small engines, not too many 2 strokes but enough to be dangerous. 

I bought an ms280 on auction site unseen, won't do that again unless it's a screaming deal. Was planning on getting running and selling, but probably won't get money back out of it so just keep it for a backup saw... if I can get it running properly. 

I put a carb kit in and new plug, top of piston and cylinder looked ok from what I could see. The spark arrestor screen was clear but I could not get it to run. I pulled the muffler off and it looked clear, but cut it apart and drilled out the holes to 3/8. I had the saw running with no muffler, ran like a scalded ape. Put muffler back on and would not start. Took muffler off, and fired up. Went through this process 2 or 3 times. Took muffler off, started it, set saw down and went to set muffler on. As soon as I got it up to the jug it died. 

I could just gut it completely I suppose but the noise level would be extreme even with ear pro for any extended period of time. I don't know what else to do or what to check without a full teardown. The carb does not have much for adjustments. No low/ high idle adjustments. Just 1 that will turn about 3/4 of a full turn. It's the one in the recessed hole above the main idle speed screw.

Any ideas or things to check, would be much appreciated!