“It runs at high idle and then it quits running”
Everyone is correct that it sounds like an air leak, and I agree. A pressure and vac test will tell the tale, but remember that this is an MS361. Where do most MS361’s have air leaks? The impulse hose!
These saws are getting old, but I rarely see bad bearings or seals. What I find several times a year is an impulse hose that has come off the handle housing side nipple. The impulse hose on this model isn’t a ribbed type hose, but a length of 0712-923-8004 fuel hose. It’s not as resilient as the ribbed hoses, and experiences all the flexing, heat, cold, and vibration that occurs between the engine and the tank housing.
I see this failure so often that I replace the impulse hose when I service the MS361. Call it preventative maintenance. The hose can usually be replaced without removing the tank housing. The engine side end can be a real bast#%d to get off the crankcase nipple, but other than that it is a simple job.
I’m a big fan of going after the low-hanging fruit. You can see a disconnected impulse line with only a flashlight. If it’s disconnected, replace it. If there are still running issues, do a P and V test to find any other crankcase sealing issues that may exist.