Komatsu Engine Idler Gear 6128-21-4321

Komatsu Engine Idler Gear 6128-21-4321 is a Komatsu engine replacement part listed by 19PARTS for engine-section lookup, hub navigation, and part-number verification.

Product overview

Part number 6128-21-4321 is listed as Idler Gear. Search also by the no-dash alternate number 6128214321.

Engine book references

This part appears in Komatsu engine parts book paths such as:

• ENGINES / S4D155-4 S/N 10287-50040 / CYLINDER BLOCK / POWER TAKE OFF(#10287-) (225)
• ENGINES / S6D125-1CC S/N 22313-UP / CYLINDER BLOCK / POWER TAKE OFF (0225)
• ENGINES / S6D125-1CC-C S/N 22313-UP / CYLINDER BLOCK / POWER TAKE OFF (0225)
• ENGINES / S6D125-1CC-FC S/N 10001-UP / ENGINE / POWER TAKE OFF(#22313-) (A2250-01A5)
• ENGINES / S6D125-1CC-FW S/N 10001-UP / ENGINE / POWER TAKE OFF(#22313-) (A2250-01A5)
• ENGINES / S6D125E-2C-6 S/N 60721-UP / ENGINE / POWER TAKE OFF(#60863-) (A2210-B3B1)

This part appears in 27 Komatsu engine book paths in our reference data.

Verification note

Always confirm final fitment by engine model, serial range, diagram callout, and part number before ordering. Hub references are provided to help buyers find the right engine section and related parts faster.

Keep Ops Moving

19PARTS organizes Komatsu engine parts around searchable engine-model hubs so rebuild shops, equipment owners, and fleet teams can identify parts and keep repairs moving.