Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

Hello, I recently purchased a Dayton Portable Generator powered by a Honda GX390 motor. First, Dayton sent the wrong engine manual with the unit. Second, I looked up the manual online to find that the oil level in the motor is critical. I filled the engine today with oil and noticed that there are NO markings on the dipstick indicating high and low engine oil levels, only x's up and down the entire length of the stick. The online manual specified an upper and lower marking...what's up with that? How am I supposed to ensure there is sufficient oil or prevent overfilling the engine if there are no markings? Thank you.

I assuming that this gx390 does not have an extended oil fill tube and the oil fill cap is near the bottom of the motor like on most of the gx series.   If that is the case i don't believe it is possible to overfill the engine with oil as before an overfill would happen the oil would be overflowing the fill hole.   I usually fill my gx motors to the bottom of the threads of the fill hole with the engine level.

The oil is full when is just touches the upper hash marks on the dip stick. You have to unscrew the dip stick, wipe it clean but do not screw it back into the fill port. You're supposed to line up the dip stick like you would if you were going to screw it back into the fill port (without actually screwing it back in) and then check the oil level. I have a GX390 on my new Honda EM6500SX Generator and pages 43 (Engine Oil Check) & 44 (Change Engine Oil) in the Servicing your Generator section provides a drawing showing exactly how to check and change the oil.

Here's a link to the manual. You may have to do a copy and paste: http://powerequipment.honda.com/pdf/manuals/00X31Z236000.pdf