164090 Idler Flat Pulley Compatible with RFM Series 4' 5' 6' Finish Mowers, Lawn Tractor Pulley Replaces King Kutter Part (1 PC)

What It Is

The 164090 Idler Flat Pulley is a replacement tension pulley designed for mid-mount finish mowers, specifically the RFM (Rear Finish Mower) Series in 4’, 5’, and 6’ cutting widths. It guides and tensions the mower deck belt on lawn tractors, ensuring proper blade engagement and belt longevity.

Fitment & Compatibility

Before buying, verify these three things:

• Deck size and model: Confirmed fit for King Kutter RFM Series 4’, 5’, and 6’ finish mowers (e.g., RFM-48, RFM-60, RFM-72). Also compatible with many generic lawn tractor decks using a flat idler pulley of this size.
• OEM part number: Replaces King Kutter part 164090. Cross-check your mower’s original pulley part number—this is an aftermarket replacement, not OEM.
• Measurements: The pulley is flat (not grooved) with a 4-inch outer diameter and a 5/8-inch bore. Measure your existing pulley’s diameter and shaft diameter to confirm. The flat face means it’s for belt backside contact, not V-belt grooves.
• Mounting: Uses a standard bolt and spacer (not included). Check that your mower’s idler arm and hardware match this bore size.

Key Things to Know

• Quality: Basic steel construction. Good for light-duty residential use; may wear faster under heavy commercial use or high debris conditions. Not sealed bearings—keep clean and lubricated.
• Installation: Easy to swap—remove one bolt, replace pulley, reinstall. No special tools needed. Takes 10–20 minutes.
• Common gotchas: The flat face can slip if belt tension is too low or if the pulley gets glazed from heat. Check belt condition and tension after install. Also, verify the spacer or bushing from your old pulley fits; new pulley may not include one.
• Fitment variance: Some RFM models use a different bore or diameter. Measure twice—mismatched bore will cause wobble or failure.

Should You Buy It

Buy this if you need a budget-friendly, direct replacement for a worn idler pulley on a King Kutter RFM finish mower and your measurements match exactly. It’s a solid choice for homeowners maintaining a 4’–6’ deck. Skip it if you need OEM-grade durability for heavy commercial mowing or if your deck uses a grooved or different-sized pulley.