Operation and Maintenance of the GD320/410

The GD320 and GD410 may be getting long in the tooth, but these diesel Honda motors are still found in a lot of power equipment. Here’s what you need to know to use yours properly and keep it running for years to come.

Before Starting

Engine oil: Remove the dipstick/filler cap, wipe it clean, and reinsert it into the engine without screwing it down. Check the oil level on the dipstick: if it’s low, add some oil. Honda recommends 10W40 made for diesel engines. Screw the dipstick back into the motor.

Fuel: To check the amount of fuel, look at the gauge window next to the fuel tank cap. These engines use diesel fuel. #2 Diesel should be used at temperatures above 40°F (4°C) and #1 diesel at temperatures below 40°F (4°C) or altitudes above 5,000 feet (1,500 m).

Air cleaner: Check the air filter elements and the air cyclone, cleaning or replacing them as necessary.

Starting the Engine

  1. Move the stop lever to “Start.” On some models, this is a separate lever in front of the throttle control, while others combine stop and throttle control into one lever.
  2. If the engine has an electric starter, flip the decompression lever up. If it has a pull starter, pull the grip until resistance is felt, then return the grip to the starter.
  3. Push the starter button (electric starter models) or give the starter grip a quick tug (pull start models.) The engine should start.

Adjust the engine speed using the control lever. If the engine is cold, move the lever to the warm-up setting, between the “High” and “Low” speed settings.

When using an electric start, never have the start button held down for more than 5 seconds, and allow at least 10 seconds between starts. If the battery is low or dead, start the motor using the pull starter.

Stopping the Engine

Move the stop lever to the “stop” position. If the motor has an electric starter, turn the ignition switch to “off.”

Maintenance Schedule

First month or 20 hours: Change the oil.
Every three months: Check the fuel tank for water.
Every 6 months or 100 hours: Change the oil and clean the oil filter, foam air filter and spark arrester (if equipped).
Every year or 300 hours: Change the air cleaner.
Every two years or 500 hours: Have a repair shop check the injection nozzle and fasteners, and clean the fuel tank.
Every three years or 1,000 hours: Have a repair shop change the fuel filter and inspect the combustion chamber.

Changing the Oil

To drain the oil, remove the drain bolt on the base of the engine and let the used oil empty into a suitable container. Once the engine is empty, screw the drain bolt and washer back in.

If the oil filter needs to be serviced, remove it from the engine after the oil has been drained: unscrew the two 6mm bolts on the cover, located opposite of the drain plug, and slide out the spring and filter. Rinse off the filter with a nonflammable solvent. Once it’s dry, reinstall the filter with the spring and oil seal between the filter and the cover.

To add oil, remove the oil cap/dipstick and add oil through the filler neck until it comes up to the edge of the neck. The GD320 holds 1.22 quarts (1.15 L) of oil while the GD410 holds 1.32 quarts (1.25 L).

Air Cleaner

Access the cleaner by removing the wing nut and cover, followed by another wing nut and grommet. The paper and foam filter elements should slide off. Wash the foam element in soap and water or a nonflammable solvent, then once it’s dry, soak it in clean engine oil and squeeze out any excess. Reassemble in reverse order.

To clean the cyclone housing, unscrew it from the bottom of the air cleaner cover. Rinse the cyclone housing and air guide with water and allow them to dry. Reinstall the housing, making sure the air guide is sitting so that the widest part of the fins are at the bottom.

Removing Water from the Fuel Tank

When water mixes with diesel fuel, it separates, settling at the bottom of the tank. To remove this water, loosen the fuel tank drain bolt, located on the front left side of the tank until the water drain hole is exposed. Water should trickle out of this hole. Once the water stream is replaced by fuel, tighten the bolt.

Spark Arrester (If Equipped)

Wait at least a half hour after the motor has been run to ensure the muffler is cool.

Remove the three bolts and one nut holding the muffler onto the engine, then remove the three nuts holding the arrester onto the muffler. Use a wire brush to clean off any carbon deposits. Replace the arrester if it has any holes or signs of cracking. Reassemble in reverse order.

Where to Buy Honda Engine Parts

When you need parts for one of Honda’s small engines, visit Honda Lawn Parts. We’re a factory certified dealer for Honda power equipment ranging from stand-alone engines to riding lawn mowers, including older equipment like the GD series.

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