YONG HENG PCP Air Compressor 4500 PSI Air Compressor Piston Slop

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FIDI_G

FIDI_G

Member
Feb 1, 2023
301
160
Atlanta GA
Hey guys,
Against my better judgement I bought a used Yong Heng 4500 compressor that's about a year old for $75. According to the person I bought it from all it needed was a cylinder gasket and air gauge manometer. Famous last words lol. Anyway going over everything and looking closer at the piston / rod setup it appears to be a bunch of slop in the wrist pin area. I also noticed that the two pieces of plastic 1/2" washers' where the wrist pin slides through on the underside of the piston are both on one side. Does this sound right? Please look at my video and tell me if this looks right. I just need someone that has actually done this and have first hand experience with this chime in.

 
Yeah ID say its worn and the source of the piston slop. Look how wollowed out the connecting rod is. Wow

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It looks to me that the burst disk is leaking but not blown completely. Seeings how the con road small end is just plain wore out I'd get a whole new top end with the con road. How does the crank pin look? I loos to me as if it got either real low on oil or he used some really crappy oil or even never changed it. Also check to make sure there's no play in the crank bearing by trying to move it up and down along with side to side.
 
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DesertSilver said:
It looks to me that the burst disk is leaking but not blown completely. Seeings how the con road small end is just plain wore out I'd get a whole new top end with the con road. How does the crank pin look? I loos to me as if it got either real low on oil or he used some really crappy oil or even never changed it. Also check to make sure there's no play in the crank bearing by trying to move it up and down along with side to side.
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The pin is fine but look at how wollowed out the connecting rod is. I have a new rod / piston on order. Should be here in a few days. Crank bearing seems ok no slop in there. I also swapped to Purple oil and did an oil change. So I should also get a whe new brass burst disk thing? Not just the disk but that hole assembly?

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FIDI_G said:
Next delima with my HS ive got a massive air leak here. Comming from the brass cap.its got a tiny little hole not sure if thats whats venting? Is there an oring thats supposed to be in there sealing things up. It does have a little brass disk with a small little rounded connector thingy.


Anyone???

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I had an issue with the burst safety screw leaking a while ago. I changed the safety disk and it was still leaking so I replaced it again and nothing changed. It turned out on my end that the problem was actually the brass washer that holds the disk in place. Somehow it had 3 hairline fractures that were almost impossible to see with naked eye. Once i replaced that as i have extra the leaking stopped. Hope that helps. As for the other fittings with the tubes, I just applied a bit more pressure to tighten them up and all was and still is well.
 
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So after much tweaking and another late nite Im at a loss. I was able to find a small disc in my bag of spares and replaced the burst disc. I manged to get rid of all apperant leaks. I replaced both gaskets on head. I cant get compression above 1800. See pics and video. I thought I had made major progress but it wont go above 1800psi. See pics. Its been running for 10 minutes now with very little progress.

1) how long should it take to go from 200 bar to 300 bar?

2) how hot should this get before I turn it off?
What temp?

3) should I just shut it off at 15min? Let it cool for 30 and restart?

Recap:
Look at pics both gun and compressor hovering at those settings and compressor has bden running for 15min. Something is up.

Let me know what you guys think..


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caseybry said:
No that is definitely not right there when you assemble it there is a slight bit of play about 2000s. Google young hang piston and rod. And order it. I think it cost me 35 bucks for the connecting rod and pissed and then I bought.
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They are by far one of the best compressors out there. If you use water with ice in it to cool it. I have had mine for 3 years. Up until 6 months ago I used it a lot. Probably six times a day to fill a gun. I always used ice water which kept them seals very cool and the primary piston. I have not had to put new seals on the primary and it's been 3 years I've been using that compressor. So once you get it together as you get to do is keep the heat down.
 
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caseybry said:
No that is definitely not right there when you assemble it there is a slight bit of play about 2000s. Google young hang piston and rod. And order it. I think it cost me 35 bucks for the connecting rod and pissed and then I bought.
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yes I have one on order it should be here in a few days and will swap it out. Ill stop messing with it until it comes in. Yes I have been using ice water to cool it.

Not sure if I mentioned this but bought this used in non working condition. I over paid lol at $75 used. The head was loose and gasket missing when I got it. So far Im going to replace air gauge, piston connecting rod, head gaskets, oil, burst disc (the one I replaced is sketch) WM is kind enough to send a few over as this is an issue.

Not complaining I like a project and love tinkering on stuff like this. Im approaching the could have bought one new price but thats Ok if I can get it working with a new piston rod combo. Ill be happy and its been a good learning experience. Nothing like jumping in with both feet into the deep end.

Thanks again for everyones help. Ill update again in a few days once I swap out the piston rod and burst disk.

Whats the best practice to run this? 15 minutes at a time? Whats the cut off temp?
 
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Heavyopp said:
48 isn’t hot but you shouldn’t have seen that just filling a gun.

Are you sure the pump works?
Do you have the intake adjustment open on the pump?
Is it the pump supplied with the yong heng?

There is an adjustment knob on the pump, opens or closes the water intake - be sure its full open
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Yeah the valve on the pump is fully open. Its the stock water pump. I can see the water flowing its no jet stream but it flows OK.

There is a new piston and rod. The compression is really tight. Does it need to break in a bit?? I did do one test with the closed valve and brought the psi up to 4000. Then turned it off listened for leaks waited a minute to see if there were leaks and slowly released the pressure. Then I let it cool down a bit and filled my gun. I have a laser thermometer I used for my rc trucks ill check the temp on the head and see if its accurate.
 
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I ran it 6 times today. I filled to 280 bar and shot down to about 130 bar. I do have a few leaks still but very small. It only takes a few minutes to charge but it still gets to 50c by the time it reaches 280 bar.

I did use my laser thermometer and its a few degrees different than the internal meter.

Should I rebuild the top part of the head or just send it?
 
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