CUB CADET 917-05121 Electric Pto Clutch RZT SX ZT1 Ultima 42 S L L42 717-05121

What It Is

This is an OEM electric PTO clutch for Cub Cadet zero-turn mowers, engaging the blades via an electromagnetic field when you flip the switch. It’s designed for RZT, SX, ZT1, and Ultima series models with 42-inch or 50-inch decks.

Fitment & Compatibility

Before buying, confirm your mower’s model number and deck size. This clutch (part 917-05121) replaces 717-05121 and fits Cub Cadet RZT S 42, SX 42, ZT1 42/50, Ultima ZT1 42/50, and L42 series. Measure the old clutch’s bolt pattern (typically 3 holes on 4-inch centers) and shaft diameter (usually 1 inch). Check that the pulley diameter matches your belt—common sizes are 4.5 or 5 inches. Verify the electrical connector type (two-wire flat or round pins) to avoid wiring mismatches. Not compatible with older RZT models with 54-inch decks or non-Cub Cadet brands.

Key Things to Know

• Quality: OEM part from Cub Cadet, so fit and electrical specs are exact—but the 3.4 rating suggests some users report early failure or noise. Inspect for damage on arrival.
• Installation Difficulty: Moderate. You’ll need a puller to remove the old clutch from the engine shaft, a torque wrench (typical spec 35-45 ft-lbs for the center bolt), and basic wiring skills. Expect 1-2 hours.
• Common Gotchas: The air gap between clutch and rotor must be set to 0.010–0.015 inches—too tight or loose causes slipping or drag. Also, the pulley may be directional; mark belt rotation before removal.
• Warranty: Often 90 days to 1 year from Cub Cadet, but verify with seller—some aftermarket versions offer longer coverage for less money.

Should You Buy It

Buy this if you want a guaranteed OEM fit for your Cub Cadet ZT1 or Ultima and don’t mind the premium price. But if you’re on a budget or your mower is older, consider a high-rated aftermarket clutch (e.g., Stens or Rotary) with equal specs—check reviews carefully, as fitment and durability vary.