My Honda GCV160 mower is giving me problems. When I move the throttle control lever to max, it pushes back and moves on its own down to half throttle or lower. This is mostly a problem in tall grass when I need the power, but sometimes even with no workload it will throttle itself back until it dies.
Is this governor, carburetor, throttle control, or something else? I can replace all these things except I’ve never tuned a governor before. Just need a push in the right direction.
It sounds like cleaning/replacing the carb is the way to go. You need to clean out the jets, or usually for under $20 you can get a new one. Happy mowing.
Question: If you hold the throttle control in place does the engine still “throttle back”? If no, it sounds to me like you have a throttle control/cable problem. If yes, then something’s wrong with the engine.
It doesn’t throttle back if I hold it. In fact that’s how I maintain higher speed in deep grass, I have to keep one hand pushing the throttle to max or else it will throttle down and stop.
In my opinion, the governor is not the issue. The governor prevents the engine from over-revving, but gives it more gas if the engine speed drops to bring the speed back up. Neither is the problem likely to be in the carburetor. Do you know how old the engine is (as is, when was it built) and how long you have had it?
It sounds as if your throttle cable does not have enough resistance to movement. I suspect the throttle return spring is overcoming the resistance in the throttle cable, and closing it. I am not all that familiar with the GVC160 engine, but I do have a GVC140. There may be differences in the models. I just replaced the throttle control on mine and I discovered that there is a nut on the bolt that the throttle lever pivots (on the handle of the mower). The tightness of this nut controls how easy it is to move the lever. If yours is similar, you might try tightening it a bit (maybe an eighth of a turn) and see if it helps.
Or, it could be something else, altogether.
Funny, this is exactly what I was suspecting. I just felt like it was a noob diagnosis to see the throttle lever moving and conclude that the lever is broken 
Plus I stripped the screw trying to tighten the exact thing you were talking about, so I’ll have to revisit.
It’s an old machine, I think 10 years old. I really need to ditch it and go electric, but right now cash is tight and I already made small investments in new throttle lever & cable, carburetor, spark plug, and air filter.
I was thinking throttle cable/return spring, too, but … how cool would it be if this was your issue, too:
If your lever and detents are working properly and it’s still throwing the lever out of position on its own, then it would /almost have to/ be cable, linkage, or return spring issues.
Maybe 
Or, it could be something else.
