Chainsaw Repair

my husqvarna k 750 is dies During Cut Concrete it the blade During Cut Concrete enters 2 cm and the blade stop the Bearing right i changed the clutch and the coil and the cylindr and the piston and i made a hole in the exhaust and no usless and i changed the plug and i changed the carb and i opend the gas cap and i changed the gas filter and the air filtet and i face the same problem

one of them past through our workshop with same problem a few years ago ,i think it had a hair line crack in crankcase our lad said that worked on it

On cutoff saws it is absolutely critical that the air filter seals 100% perfectly,if the motor ingests any concrete dust ot metal dust the cylinder and piston will wear out extremely quickly. On cutoff saws check the piston intake skirt(pull off the carb and look with a light) if you see any scratches at all pull off the cylinder and check the nikasil plating below the intake port,it can be worn away to the aluminum. Ingesting abrasive particles is what kills most cutoff saws.
All sealing surfaces of the air filters should be sealed with a thick heavy grease like wheel bearing grease.
Like the other guys said,if it's quitting when hot it could be the ignition or a bad tank vent. Just replace the vent to eliminate that possibility. Also when it quits immediately check it for spark.