For me it is an older Yardman with Briggs V twin that in round one was the engine quit while mowing his lawn Found that customer had removed the carb and lost the fuel valve and has replaced it with one from a tecumseh kit. Customer had lost the 4 mounting nut for the air cleaner to carb. Had removed the old metal square fuel pump and disassembled it and lost the nuts hold the parts together. Replaced with E bay fuel pump that was hooked up backwards. Governor springs were disconnected and then stretched out of shape and reconnected to other thinks other than the governor arm and throttle control. Upon reversing everything that the customer did found that the reason may of been a damaged O ring in the carb. Returned to customer
Round two. After customer used the mower to mower his lawn, engine rev's out of control. Customer bends carb linkage to remove it from the governor arm and then twist it 90 degrees and connects it to one of the holes on the rotating throttle control. Found parts of governor gear laying in oil pan. Upon reinstalling engine found that the customer had tightened the starter cable and had twisted the terminal which then broke the brush wire.
Current project is a 2016 Hisun 550 that the customer said was running and backfired, died and the wouldn't restart. After setting at Rural King for 3 months, customer decided to bring it to me. According to customer Rural king replaced the fuel injector due to a injector code, and replaced the coil. It was claimed that they had checked the timing and it was correct. Initial crank at my shop caused a puff out of the intake and then no compression. Timing chain has jumped off of the crankshaft timing sprocket. Due to engine location in the frame may not have enough space to remove the flywheel crankcase cover without removing the engine from the frame. And injector code may or may not be from the jumped timing. So could be a separate issue that depending on cause could still need a diagnosis and repair after tearing down the engine and replacing the timing chain.