951-14423 Carburetor for Cub Cadet SC100 SC300 SC500 ST100 LE100 SC300HW SC500HW 159CC 5X65RU Engine for Troy Bilt TB105 TB120 TB220 TB270 Lawn Mower MTD RM120 RM210 RM220

What It Is

This is an aftermarket carburetor assembly for 159cc single-cylinder engines found on Cub Cadet, Troy-Bilt, and MTD walk-behind mowers. It replaces the OEM carb on models like the Cub Cadet SC300, SC500, ST100, and Troy-Bilt TB105, TB220, TB270.

Fitment & Compatibility

• Engine check: Must be a 159cc 5X65RU engine (check engine shroud or manual). Not for larger or smaller engines.
• Model list: Fits Cub Cadet SC100, SC300, SC500, SC300HW, SC500HW, ST100, LE100; Troy-Bilt TB105, TB120, TB220, TB270; MTD RM120, RM210, RM220. Verify your specific model number tag under the seat or on the deck.
• Deck size: Irrelevant—this part goes on the engine, not the deck. Measure the bolt pattern: two mounting studs spaced 60mm center-to-center.
• OEM vs aftermarket: This is a non-OEM replacement. It includes the carb body, gaskets, and sometimes a fuel line. It does not include the air filter or primer bulb—reuse your old ones if they’re clean.
• Measurement: The fuel inlet is 1/4" barb. Ensure your fuel line is 1/4" ID or use the included adapter.

Key Things to Know

• Quality variance: Aftermarket carb gaskets can be thin or poorly cut. Inspect them and consider using a thin layer of gas-resistant sealant if they don’t sit flat.
• Installation difficulty: Moderate. You’ll need to remove the air filter housing, disconnect the throttle/governor spring, and swap the carb. Expect 30-60 minutes if you’ve done it before; 90+ minutes for a first-timer.
• Common gotcha: The choke linkage may be stiff or misaligned out of the box. Bend it gently with pliers to match your old carb’s travel. If the engine won’t start, check that the float isn’t stuck (tap the bowl lightly).
• Fuel system prep: Clean or replace the fuel filter and drain old gas before installing. Stale fuel or debris will clog the new carb quickly.

Should You Buy It

Buy this if your mower won’t start or runs rough due to a clogged or warped OEM carb, and you want a budget fix under $20. It’s a solid value for DIYers who can handle basic carb swaps. Skip it if you need exact OEM fitment or have a complex governor setup—stick with a genuine Cub Cadet or Briggs & Stratton carb for worry-free compatibility.