Daihatsu Hijet — Carburetor

Rebuild kit numbers, mixture screw baseline, idle adjustment, and lean/rich diagnosis.

The EF-NS uses an Aisan/Mikuni-style carburetor. Three carb numbers were used across the production run — rebuild kits are available for each. Match the kit to the number cast on your carburetor body.

Rebuild Kits

Carburetor Rebuild Kits by Carb Number

Brand	Part Number	Notes / Info
Aftermarket	21100-87702 kit	Rebuild kit for carb 21100-87702
Aftermarket	21100-87710 kit	Rebuild kit for carb 21100-87710
Aftermarket	21100-87729 kit	Rebuild kit for carb 21100-87729

Baseline Settings

Mixture Screw — Starting Baseline

2.5 turns out

Idle Speed (warm, choke open)

950 RPM

Target CO

1.5% (+1.0% / −0.5%)

Target HC

Below 900 PPM

Tip:After a rebuild, lightly seat the mixture screw — do not overtighten or you will score the brass tip — then back it out exactly 2.5 turns. This is the starting baseline. Once the engine is fully warm and the automatic choke has opened completely, set the idle speed screw to 950 RPM. Fine-tune the mixture screw from there: richer (out) for a stumbling idle, leaner (in) for a hunting idle.

Idle Adjustment Procedure

Warm the engine fully — the automatic choke must be completely open before adjusting. This takes at least 10 minutes of running.
With the engine at operating temperature, locate the idle speed screw on the carburetor body. Turn it in to raise idle, out to lower. Set to 950 RPM.
Turn the mixture screw in (lean) slowly, in ¼-turn increments. The idle should rise slightly as mixture improves, then fall and stumble as it goes too lean. Find the point of highest idle speed.
From that point, back the mixture screw out (richer) ¼ turn. This is the correct setting.
Re-check and readjust the idle speed to 950 RPM after finalizing the mixture.

Lean vs. Rich Diagnosis

Condition	Symptoms	Plug Appearance
Lean	Weak, fluctuating idle — stumbling under acceleration	White or very light gray porcelain
Rich	Black sooty exhaust — stumbling off idle — poor fuel economy	Black, carbon-fouled

Warning:If the catalytic converter temperature warning light (the “barbecue light”) illuminates, the engine is running rich and dumping raw fuel into the exhaust. Fix the mixture or repair the automatic choke — the converter substrate is at risk of overheating. Do not tape over the light.

EVAP Canister Flooding

Topping off the fuel tank after the pump nozzle clicks off is the most common cause of a flooded canister. Raw liquid fuel gets forced into the charcoal canister and physically blocks tank venting.

Symptoms of a saturated EVAP canister:

Strong fuel smell around the vehicle
Pump nozzle clicks off after filling only ~1 gallon
Pressurized hiss when the fuel cap is removed
Rich running, stalling, or no-start after fueling

A saturated canister cannot vent the tank, causing pressure to build until the carburetor float needle is forced off its seat and floods the intake with raw fuel. Replace the charcoal canister (OEM 77704-97501) — a saturated canister cannot be dried out, the activated carbon is permanently contaminated.

Danger:Never spray carburetor cleaner into the vacuum lines or actuator port. The solvents will dissolve the rubber check valves and actuator diaphragm immediately, causing irreversible 4WD system failure.