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Dale Gribble 09-03-2013 03:13 PM

Honda gx390 throttle stays wide open
I have a Honda GX390 on a pressure washer I'm trying to get working. The engine is in good shape. I just replaced the carburetor and throttle linkage/springs. She starts on one pull, but runs wide open, regardless of where I move the throttle lever.

First I tried a static adjustment: I removed the gas tank. At the top of the block, where the governor arm attaches to the governor post I loosened the pinch nut, held the throttle wide open, turned the governor post clockwise as far as I could, and tightened the pinch nut down.

That didn't fix the problem. So I replaced the governor gear inside the crankcase. I also removed the governor arm and inspected it. I removed some rust & corrosion from the top of the post where it attaches to the arm, reconnected and did another static adjustment.

Still starts on one pull and runs wide open. If I move the governor rod (that attaches from the gov arm to the carburetor) by hand, I can lower the rpms. Moving the throttle arm does nothing.

At rest (with the throttle arm in idle position) the linkage is such that the governor arm defaults away from the carb, pulling the throttle shutter open.

Moving the throttle lever to the left should stretch the spring and pivot the governor arm so as to pull the rod away from the carb, opening the shutter.

Throttle arm and spring act as they should, but since the governor arm is already in that position, it causes no movement in the gov arm.

What could the problem be? Am I doing the static adjustment right? Do I need a new governor arm? Throttle lever? Any ideas? because I'm stumped. Thanks.

Dale Gribble 09-04-2013 12:43 AM

Umm. So I did another static adjustment. This time I turned the governor shaft counterclockwise while holding the governor arm in WOT. Runs nice now.

Makes me wonder if I even needed to get into the crankcase and replace the governor gear.


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