MTD 420cc - User Manual

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MTD LLC, P.O. BOX 361131 CLEVELAND, OHIO 44136-0019

Printed In USA

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Op e r a t O r ’s Ma n u a l

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Form No. 769-06053A

(March 3, 2011)

Questions and Answers

M
Melissa WatersJul 27, 2025
Why does my MTD 420cc Engine fail to start?
- C
  Colleen SmithJul 27, 2025
  Your MTD Engine might fail to start due to several reasons. It could be flooded, in which case you should wait at least 10 minutes before attempting to start it again. Other potential causes include a disconnected spark plug wire (connect it to the spark plug), an empty fuel tank or stale fuel (fill the tank with clean, fresh gasoline), the engine not being choked (choke the engine), a faulty spark plug (clean, adjust the gap, or replace it), or the throttle being in the stop position (move the throttle to the FAST/Run position).
J
jared62Aug 10, 2025
What to do if MTD 420cc runs erratically?
- M
  melissa52Aug 10, 2025
  If your MTD Engine runs erratically, check the following: Ensure the spark plug wire is securely connected and tightened. If the spark plug is scorched, defective, or has an incorrect electrode gap, readjust the gap or replace the plug. Stale fuel can also cause this issue, so replace it with clean, fresh gasoline. Make sure the engine isn't running with the choke on; if it is, move the choke to the off position. Lastly, check for water or dirt in the fuel system; if present, drain the fuel tank and refill with fresh fuel.

Summary

Important Safe Operation Practices

Preparation

Safe Handling of Gasoline

Precautions for handling gasoline to prevent fire and explosion risks.

Maintenance & Storage

Keep the engine in safe working order

Do not modify engine

Warning against altering engine settings or components.

Safety Symbols

Set-Up

Oil & Fuel Specifications

Recommended oil types and fuel grades for engine operation.

Checking Oil Level

Procedure for checking the engine oil level before operation.

Filling Oil Sump

Instructions for adding oil to the engine's sump.

Fuel Recommendations

Adding Fuel

Step-by-step guide for safely adding fuel to the engine.

Controls and Features

Engine Controls Overview

Identification and function of various engine controls.

Operation

Pre-Operation Check

Essential checks to perform before starting the engine.

Starting the Engine

Instructions for safely starting the engine.

Engines With Electric Starters

Engines with Recoil Starters

Stopping the Engine & Short Term Storage

Maintenance

Maintenance Schedule

Overview of required maintenance tasks and intervals.

Oil Recommendations

Guidance on oil types and viscosity for engine maintenance.

Checking and Changing the Oil

Detailed steps for checking and changing engine oil.

Spark Plug Service

Procedure for inspecting, cleaning, and replacing the spark plug.

Air Filter

Adjustments

Carburetor

Engine Speed

Fuel Storage

Extended Storage

Off-Season Storage

Troubleshooting

Replacement Parts

MTD 420cc Specifications

General

Engine Displacement	420cc
Fuel System	Carburetor
Lubrication System	Splash
Bore x Stroke	90mm x 66mm
Oil Capacity	1.1 liters
Cooling System	Air Cooled
Starting System	Recoil
Dry Weight	35 kg