Inspection - MTD 450 Series Shop Manual

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Inspection

The inspection of chain case parts is just a visual check, with some fit checking by feel. Precision measurement
is not required.
When damage is identified, the repair is not complete until the root cause of the damage is found and fixed, so
that the damage will not happen again.
When damage to a contact surface is found, replace the mating part that the surface comes in contact with. If a
gear tooth is damaged, replace the gear that it rides against. If a shaft is damaged, replace the gear or bearing that
rides on the damaged portion of the shaft.
1. Gear teeth: Replace any gear with teeth that show a significant amount of damage to the teeth.
• Chipped or broken teeth
• Fretting
• Wear
2. Gear drive features: Replace any gear with drive features that show a significant amount of damage.
• Rounded corners that should be straight
• Visible wear or looseness of fit
• Any damage that would cause a bind so that the gear does not engage or disengage easily.
• Cracks in the body of the gear
3. Gear bearing surfaces: Replace any gear with bearing damage.
• Scoring or galling on the thrust surface of the gear that can not be cleaned-up with a light dressing.
• Plain bearings within the gear that show scoring or wear.
• Needle bearings that show any visible damage or do not turn smoothly.
• Bearing damage indicated by the condition of the shaft that the gear rotates on.
4. Shafts: Replace any shaft that has significant damage.
• Bending that shows-up when the shaft is rolled on a flat surface.
• Any scoring that is deep enough to catch a fingernail
• Any wear that will interfere with bearing or seal fit
• Any wear that will interfere with the movement of a sliding part, such as the input spur gear.
• Any wear that will effect the mesh of gear supported by the shaft with the gears that they drive or are
driven by.
• Any stripped threads that will prevent fasteners from being properly installed.
5. Chains and sprockets: Replace any:
• Chain that is rusty.
• Chain or sprocket that is broken.
• Chain that is too loose.
• Chain that is too stiff to work smoothly.
• Sprocket that has teeth that are worn down far enough to make the teeth pointy.
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Chain Case
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