I am swapping over my old pump (northern tool) 5gpm 3k to an Udor BKD 5.0/36s with a K7 unloader powered by gx390. Photos show how I have it plumbed. I’ve read through the threads and set up my previous k7 on the old pump and ran it for 3 years without any issues. I used a gauge and the trickle method and continue to get surging every time I let off the trigger. I tried setting it with only 100’ of hose and then 250’ which is max I run and still same issue. I’m only pushing about 2,800 psi according to the gauge. Any input would be much appreciated.
no idea, except I’ve heard and likely I’ll never own one of these, the unloader needs to be sitting vertical, not horizontal.
your carb could just need some cleaning could be the issue.
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I’m no expert but at a glance it sounds like the unloader is cycling (it can’t decide if you are on or off the trigger). The engine is seeing less load when you’re off the trigger, so that would steer me away from engine issues aside from the fact that a GX390 is a little underpowered for what you’re tasking it with. But hey, as long as it works while you’re on the trigger just keep it pulled. Send it! Fix it when something breaks.
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Does the direction really matter? Asking in ignorance because I ran my old one the same way and seemed to work just fine. I did go out and buy a new cheaper unloader because I’ve had my fill of this project. I originally converted to gear box and was sold the wrong one and didn’t have time to wait on a new one to be ordered so I swapped back to a belt drive. Here’s an updated photo. I got some small things to do tomorrow so I can change up the unloader if needed. Thanks for your input!
man I need your bank account I can’t afford to just send it until she breaks. I was ruined by the first one I installed on my old pump. Set it up and never touched it for 3 years. Pump started taking on water so I went ahead a replaced it.
I’d rather have your bank account! I gotta put mine to work. Natty Ice doesn’t put itself in the fridge. I could be wrong but I don’t think the orientation of the unloader matters but do your own research. I’ve never had to look into it. I’ve had to patch up my rig just enough to get through the job many times but it’s alright. This stuff breaks. If it works, I send it. By the way how many cases of Mountain Dew did you have to drink to get a green GX390?
I misread that, sounds like you sent it for 3 years haha. It wasn’t in the shed.
Lol had a seafoam green truck and I painted it to match. Then wrecked the truck a couple years ago. Ahh… Such is life. Have you had the Naturdays?
You can’t set a K7 with the trickle method
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Now that’s the guy with the bank account haha. Good feller right there. No Naturdays around here (had to Google it). Natty Daddy is where it’s at. Just throw in a slice of lime & you could downstream a roof with it.
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The ZK1 can be mounted horizontal OR vertical
@PWP5gpm You need to bypass a MINIMUM of 5% for that particular unloader to operate correctly
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Sir I have no doubt you are correct, but the first one I bought I set it that way and never touched it. Matter of fact I read a response you had wrote on an old thread and went with it. 
Maybe ignorance is bliss. I did swap over to a different unloader. Do you know if it can be mounted horizontal? I assume so because it has an arrow on the bottom showing entrance. With that logic you would put it on horizontal if ran direct to pump so I’m thinking I’m okay. Have a good day sir!
5% of water flow?
I assume you can mount it anyway you like. I don’t have much experience with K7’s except to know they are problematic at best and I won’t own any more of them.
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Maybe the K7 is the wrong size.
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Yes, it should be bypassing a little bit while the trigger is pulled. I installed a ZK1 flow unloader & put a pressure gauge in line for research purposes. I started with the bolt all the way in with almost nothing coming out as per instructions. It increases pressure as the bolt is loosened by letting more water out. More water being forced out equals more pressure. The water that isn’t coming out is being bypassed. On my 6.8gpm pump with a GX630, I’ve tested it & I’m getting 6.25gpm with pressure nozzles or soap nozzles (there is no difference with sufficient horsepower). That’s with the adjuster bolt on the ZK1 backed all the way out to where it’s about to fall off. So I’m bypassing about 8 percent & the gauge shows 3000psi right off the whip. I don’t miss the Charlie Bronson recoil whatsoever.
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That’s it, I’m gonna have to get one of these. I was on a ladder today trying to soap an inset dormer and that sudden blast made my ladder move.
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If the job requires a ladder I skip it. Ain’t no low hanging fruit up there.
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If you think the ZK1 is nice in that dept. You really ought to try the ZK5. It comes on about two times slower. By my “watch” it’s like 0.8 vs 1.6 seconds. It’s nicer, trust me!
