1. Perform speed change test and cylinder misfire test, combined with auscultation, repeatedly. If the noise increases with the speed of the Bare Engine, and the abnormal noise is prominent when the throttle is shaken, it is abnormal noise in the Mitsubishi Engine bearing.

2. Perform misfire test cylinder by cylinder at idle, medium and high speed. If the sound of the cylinder is significantly weakened or disappears after the flameout, and appears immediately at the moment of re-ignition, it can be concluded that the Bare Engine bearing of the cylinder is abnormal.

3. Use a stethoscope or a long-handled screwdriver for auscultation. If the sound is not obvious, but the abnormal noise under the Mitsubishi Engine is obvious, it is abnormal noise in the Bare Engine bearing.

4. Check the oil pressure. If the abnormal noise is severe and accompanied by low oil pressure, it means that the fit clearance between the bearing and the journal is too large.