Calling all GX390 experts

Well today my gx390 let me down and left me embarrassed. Had to tuck my tail and tell the homeowners I would have to come back to finish their driveway. Basically my motor is revving high and “surging”. Hard to explain really. After I use a high pressure tip, surface cleaner, basically anything other than my jrod it starts waning and trying to recover. It flat out would not run my surface cleaner long enough for me to finish the job. So y’all that are familiar with these motors. Can you throw me out some possible problems/solutions? Or could It be my pump? So frigging frustrating. Here’s what I’ve done. I’ve checked the needle and bowl for debris. (None). Checked valves and I’m pretty sure they’re adjusted like they’re supposed to be. I will do a fluid change on motor and pump. And change the spark plug. The carb is new with only like 30 hours on it.

I’m about to say efff it and buy the 8gpm a lot sooner than I wanted. A lot of options. For mostly residential and light commercial would y’all recommend the 630 or the 690? I know I want a Honda motor. Can’t figure out which pump would be good. I’m wanting to stick with cold water but have the option to add a burner down the road. Sorry for the long post but it’s been one of those days from hell.

Run it and slowly close the choke. See what happens. Have you ever changed the fuel filter?

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No but I’m about to change every damn thing on it tomorrow lol. Oil, pump oil, spark plug, fuel filter. Recheck the valves also. My plug tip was gray so it’s running lean. When I got a new carb I just put it on and it ran great for about 30 ish hours and now this. I may try to adjust the air/fuel screw too. I like my motors to run a little rich so I didn’t like seeing the grey plug tip

I actually did that today and it would run slightly better and then die pretty quick when the choke was turned on. The motor is revving high and bouncing the throttle if that makes sense

Governor arm or spring could be the culprit.

I will begin my YouTube search now. Thanks guys. Today really took the wind out of my sails, but guess days like that happen.

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Thanks @Steve I wish they would have shown a video of the motor while it was surging but that sounds exactly like what mine is doing. That spring is moving back and forth causing my rpms to fluctuate and not hold pressure.

Thanks for the link. What is your opinion on gx630 vs 690? I’ve been looking at the specs and I see no difference that jumps out at me. What am I missing?

Fuel delivery is about only theoretical difference. But there is a lot of hotse power difference. Get the 690

@Innocentbystander what is the exact setup you would recommend for residential and wanting to get into light commercial? Cold water. This will be a big investment for me so I’m looking high and low. I really want to buy new so there are no surprises.

8gpm. 3000 psi. Non aluminum frame. Udor pump. I use Honda’s now because Koehler and Briggs wouldn’t run on ethanol. Maybe that has changed by now

So just out of curiosity, what’s the issue with aluminum frames? It seems like as long as they’re a heavy enough gauge, they would be an ideal choice since they don’t rust.

My year old pressure pro (I know, not the same quality as a Landa :roll_eyes:) is on a painted steel frame, and it’s already chipping and getting surface rust in spots.

Flex and vibration.

I know it’s not much help now (and the cynics and naysayers will huff and puff), but I keep the little Ryobi 2800 psi, 2.3 gpm pressure washer I was using when I was knocking on doors with me on every job. It was collecting dust when the pump died on my other unit about an hour into a job last month. The little Ryobi took longer (quite a bit longer) to finish the job than I wanted, but I finished it and got the check. Having a back up for my back ups has saved my butt a handful of times.

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Oh trust me I know. I have a little Honda gcv or whatever it is I let my friend “borrow” for an undetermined amount of time. I got a really nice wand and him being my “dedicated” small motor mechanic whenever i need him out of the deal. Kinda ironic right? :roll_eyes::stuck_out_tongue_winking_eye:. @Innocentbystander the link for the washer you showed me isn’t good. I can’t see a price on it. That being said any of y’all have the hook up on a 8gpm unit? Lol. I’m pretty much expecting to pay between $3200-3800. Is that about right or am I missing a killer deal somewhere?

Not sure why the link is down but he doesn’t ship anyway. Those are $4500.

I have one steel frame from 1998 from Xterior that has had a lot of pumps and motors on it over the years. It has some rust but will last me until i quit this gig.

I had the same problem and called the manufacturer and was told that it was the lack of water that was causing the surging. Come to find out there was a water flow restrictor on the faucet. Removed that and everything was fine. Some faucets in our area have them as required by the water department. I now take a pipe wrench with me on house calls and ask permission to remove the restrictor.