The Honda GX 390 is a 0.39 L 2-cylinder unleaded engine rated at 3600 rpm. It powers generator sets from Cummins/Onan, Honda, Pramac and SDMO, including the 5 GRBA 378A, 7 GRBB 377A, EM6500SX and GX390. It holds 1.16 L (0.3 gal) of oil and 40.6 L (10.7 gal) of coolant.
Also known as: Honda GX 390
Part of the Honda GX390 engine family — 2 variants share parts & fitment.
| Oil capacity | 1.16 L |
|---|---|
| Coolant capacity | 40.6 L |
| Displacement | 0.389 L |
| Cylinders | 2 |
| Aspiration | unleaded |
| Rated speed | 3600 rpm |
Shared across brands: Cummins/Onan, Honda, Pramac, SDMO
Compiled from service & troubleshooting documentation across every generator set that uses the Honda GX 390.
| Type | Item | Value | Unit | Condition |
|---|---|---|---|---|
| Other | Crank duration | 3-3-4-5 | sec | per automatic attempt sequence |
| Other | Enclosure dimensions | 85x58x33 | mm | |
| Other | Length of cable | 2 | m | |
| Other | Max. Standby Current | 9.8 | mA @ 12 V | |
| Other | Number of attempts | 4 | automatic starting attempts | |
| Other | Pause between each automatic attempt | 10 | sec | |
| Temperature | Operating Temperature Range | -30 to +70 | °C | |
| Voltage | DC supply | 12 | VDC | generator battery |
Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.
| Fluid | Grade | Standard | Ambient | Capacity | Notes |
|---|---|---|---|---|---|
| Engine oil | SAE 15W40 | Sold by SDMO in 0.5 L (RBH0,5) and 1 L (RBH1) bottles |
Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.
⚠ 10 sec start delay is used in combination with an ATS panel to prevent multiple short start-stop commands coming from the ATS panel while the mains is unstable during blackout.
Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.
| Part # | Description | Category |
|---|---|---|
| 0200-3065 | ALTERNATOR ASSEMBLY | Alternator |
| 0200-3066 | ALTERNATOR ASSEMBLY | Alternator |
| R03B | Battery Group Size: R03B | Battery |
| 0327-1230 | DIODE 1N5627 | Diode |
| 11500571 | HOLDER DIODE | Holder diode |
| 34211817 | INSUL INSERT ROTOR END CAPPIN | Insert rotor end cappin |
| 34212185 | INSUL INSERT 25MM | Insulation insert 25mm |
| 34212184 | INSUL INSERT SMM | Insulation insert smm |
| 3400042 | INSUL PYLM 200MM 3-5-3 | Insulation plym |
| 0098-6074-02 | Label, Warning | Label |
| 2081515 | LAM ROTOR P/N | Lam rotor |
| 0327-1225 | COVER-ALT | Service part / kit |
| 0327-1228 | FAN-PLASTIC | Service part / kit |
| 0327-1229 | BEARING-BALL | Service part / kit |
| 0327-1234 | RETAINER-BEARING | Service part / kit |
| 0327-1242 | END BELL-DRIVE END | Service part / kit |
| 0327-1246 | ROTOR ASSEMBLY | Service part / kit |
| 0327-1247 | END BELL-NON DRIVE END | Service part / kit |
| 11000084 | DIODE | Service part / kit |
| 11100469 | RESISTOR-VARIABLE | Service part / kit |
| 11101096 | RESISTOR-VARIABLE | Service part / kit |
| 11700883 | CAPACITOR | Service part / kit |
| 13300027 | FAN-PLASTIC | Service part / kit |
| 17130058 | STUD-STATOR (7KW) | Service part / kit |
| 23460512 | LBL ° | Service part / kit |
| 25100372 | HEAT SHIELD-MUFFLER | Service part / kit |
| 28000190 | STATOR-WOUND | Service part / kit |
| 30009010 | Pilot screw | Service part / kit |
| 36021457 | BOLT-HEX 5/16 | Service part / kit |
| 36200053 | WASHER-LOCK 5/16 | Service part / kit |
| 36200121 | WASHER-FLAT 5/16 | Service part / kit |
| 41000034 | BEARING-BALL | Service part / kit |
| 41300064 | RETAINER-BEARING | Service part / kit |
| 47000136 | ROTOR | Service part / kit |
| 47000190 | ROTOR | Service part / kit |
| 965-0532 | Generator Set | Service part / kit |
| 95/27.5 | Rated Amps | Rated current a |
| 36401078 | SCRW S/TAP 8G6X1/2 CSK CR STLZ | Screw |
| 1200046 | SHAFT ALT F86/F89 SKVA | Shaft |
| 1200084 | SHAFT ALT F86/F89 SKVA | Shaft |
| 31ZH9600 | Spark arrester screen | Spark plug |
| 34300213 | TAPE FOAM DBL SCOTCH 4008 | Tape foam double scotch |
| 34300020 | TAPE INSUL 25MM PE5I0 | Tape insulation |
| 34300021 | TAPE VIDA SHRINK 168.125MM | Tape shrink |
| 0327-1231 | VARISTOR S20K 420 | Varistor |
| 0327-1232 | VARISTOR S20K S10 USE11100469 | Varistor |
| 34700331 | VARN ISONEL 1400 | Varnish |
| 40000012 | WIRE ENAML 0.85MM PEI 2 | Wire enamal |
Parts cataloged across all variants of this engine family — verify the exact part fits your specific variant and serial number before ordering.
Parts listed by aftermarket suppliers as fitting this engine — leads compiled from supplier catalogs; verify the exact part for your serial number.
Other equipment known to use this engine, via filter-application cross-reference — useful for sourcing parts even when your exact machine isn't listed elsewhere on this page.
The Honda GX 390 engine has an oil capacity of 1.16 liters.
The Honda GX 390 has a displacement of 0.389 liters with 2 cylinders.
The Honda GX 390 powers 12 generator set(s), including Cummins/Onan 5 GRBA 378A, Cummins/Onan 7 GRBB 377A, Honda EM6500SX, Honda GX390, Pramac E8000.
A commonly reported issue on generators using the Honda GX 390 is: Engine Does Not Start. Cause: No fuel or fuel valve is not open. Fix: Add fuel/Open valve. On engine and/or under tank..