YONG HENG REBUILD PT.2!

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Gerry52

Gerry52

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Oct 13, 2017
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Oceanside,California, United States
After about 4 hours work, cleaning all parts to "sterile" condition, making sure all surfaces were devoid of scoring, gouges, etc., new piston ass'y, new gaskets, gasket sealant, reassembly, I thought I was ready to ROCK. NO SUCH LUCK! Fired up the YH, with my leak detector close at hand, looking so forward to watching the needle rise 4500psi & was only 4400psi short of that goal, ONLY!!! No leaks at any fittings or where cylinder gaskets were replaced. WTF? Very disappointing & frustrating to say the least. Took 3 weeks get the 1st gasket set. In Iimbo for now. How can it not build pressure without leaks? AARRGH!!!!!
 
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Sounds like a reed valve issue. There's also a check valve that needs to be functiong as well on the side of low pressure piston exit. Another reason I didn't use sealant on my gaskets.... I'd say check the check valve first as best you can. If you can't sort that, then check the reed valve.

Also did you check your dimensions of the heads, pistons, connecting rods? Have to wonder if you got mismatched parts. I know for sure there are two lengths of connecting rods. I think the old ones were longer, new ones are shorter. Not sure if there were any variances in the pistons or heads.....

In all fairness the gaskets aren't that big of a deal. If they tear you should be able to get them to seal using sealant. The high pressure area is oringed, so no gaskets to mess up there.
 
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I, also, thought of the Reed valve. Tearing it down should be easier now that I'm experienced but worried about the metal tubing seating less & less correctly after every tear down. I should have known it wouldn't go as easily as I'd hoped. I was extremely meticulous about all surfaces being clean & "true" but such is life in the Chinese compressor world! Thanks for the suggestions!
 
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I'm right along side with ya on my own rebuild. Couldn't build more than 3200 PSI after only 5 uses ??!!! Ordered kits for everything. Replaced piston like you did too. Cleaned everything, new O-rings and gaskets, new reed valve, lubed everything carefully during assembly. Should be like a new one, right ?? Nope. Now it will only build to 2600 PSI !!! What the heck ??!!! Checked EVERYTHING with soap like you did. Not one bubble anywhere. Ughhhhhhhh. I'm wearing the bolts OUT with so many re-assemblies. Where is the low-pressure check valve mentioned above ? at the larger tubing fitting on the discharge side of the compressor ? Any advice fellas ?? Why would it need this kind of teardown with just 5 uses ???
 
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I could see that being an issue if it wouldn't BUILD pressure. But 2600, and then stop ??!! no external signs of leakage anywhere. Just dead-headed it at my small in-line desiccant filter to help it try to build pressure fast. Nope. Not having it....... Almost everything internal has been replaced by now. Not impressed with this unit at this point. Sometimes a good deal isn't such a good deal....even though it was purchased new.....
 
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erock said:
Gerry52, sorry man..I didn't mean to hijack your post. Just frustrated...as you are too. My apologies. Hopefully somebody will chime in with solutions that we both can learn from.
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No worries pal. I don't feel hijacked. The check valve is on the right side, almost touching the pressure gauge. It's in the fitting that the tubing connects to & has the 2 dowty seals/bonded washers under it, 19mm wrench needed or a metric crescent :ROFLMAO: :unsure:. Keep pressure on it when unscrewing, there's a spring inside & a cap that makes it a check valve. I'll try to add a picture. In the pic, it's the part with the 2 #4's on it.
20231023_172756.jpg
 
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I got 3.5 years of great service from mine. Found out I'm getting "gifted" a working, double cylinder, Tuxing type compressor! Maybe my problem is solved! Still, it irks the F outa me that I did everything "right" & didn't succeed. I gotta know what it is, gifted compressor or not! That's just me.
 
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Gerry,
Sorry things didn't go smoothly. Haven't done rebuild but removed high pressure head. Stainless steel line leaked after re-assembly; tightening didn't help. Found out I'd broken bond between the hardened gray sealing "goop" and SS tubing. Made small roll (size of 2-3 grains rice, end to end) of JB Weld and wrapped around front edge of goop at SS line, then re-installed nut, leak fixed. If you go back to research further, this fix should cover leaking SS lines, should one develop. Like Long Gun's idea of possible mis-matched parts, especially since no external leaks and no pressure means internal issue. Was making 3400psi, now 100psi, something off inside, for sure. WM
 
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Honestly, the fact that the steel lines aren't leaking is pretty suspect. If they are/do, like I said, lapping compound will get those sealing surfaces to interface better.

At some point i did replace the check valve spring in mine with a weaker spring. Problem was I scored the big cylinder wall with the wrist pin cause I forgot to install one snap ring, and ran it for a little bit like that. Smoothed out the cylinder wall, and it wasnt making enough compression to open that valve anymore. I guess two small notches in the cylinder wall will do that.

I also installed the reed valve backwards once. Been using the same compressor for at least 5 yrs now. Two broken rods, broke my crank bolt 2x, crank bolt hole is galled out and literally held together with jb weld. Broke 1 piston. Reduced piston height by hand since it was smacking the top of the high pressure head (lower crank case to cylinder gasket delete, shortened head height), (dont recommend), all electrical connections are soldered now. At one point it wouldnt turn over anymore until I did that. Broke the pressure gauge, aftermarket oil filled one in use now. Front crank case gasket delete (dont recommend), necessitated modifying the front breather since it was spewing oil afterward.

Most all of my issues have been user error or negligence. Still runs great.

20220102_145322_edited.jpg
 
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Long_Gun_Dallas said:
Honestly, the fact that the steel lines aren't leaking is pretty suspect. If they are/do, like I said, lapping compound will get those sealing surfaces to interface better.

At some point i did replace the check valve spring in mine with a weaker spring. Problem was I scored the big cylinder wall with the wrist pin cause I forgot to install one snap ring, and ran it for a little bit like that. Smoothed out the cylinder wall, and it wasnt making enough compression to open that valve anymore. I guess two small notches in the cylinder wall will do that.

I also installed the reed valve backwards once. Been using the same compressor for at least 5 yrs now. Two broken rods, broke my crank bolt 2x, crank bolt hole is galled out and literally held together with jb weld. Broke 1 piston. Reduced piston height by hand since it was smacking the top of the high pressure head (lower crank case to cylinder gasket delete, shortened head height), (dont recommend), all electrical connections are soldered now. At one point it wouldnt turn over anymore until I did that. Broke the pressure gauge, aftermarket oil filled one in use now. Front crank case gasket delete (dont recommend), necessitated modifying the front breather since it was spewing oil afterward.

Most all of my issues have been user error or negligence. Still runs great.

View attachment 399473
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When you say you installed the Reed valve backwards do you mean upside down? How do you determine if it's the correct way? I used the old Reed valve because I didn't realize a new one came with the gasket set until AFTER I reassembled the YH. DUH on me!
 
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Gerry52 said:
I totally forgot I bought a 4 year warranty when I purchased the YH! Anybody on the forum have experience with warranty & return? How'd that work for you?
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Was it through a 3rd party? I believe they require you to go through a repair center, not sure if they need to be authorized or if diy repairs count.

You'd have to look at the terms and conditions set forth by your protection plan/warranty provider.

My plan excludes normal wear and tear which I think most claims could easily be denied under unless you skirt them somehow.

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-Matt
 
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I have mine for 4 years, totalling about 65 hrs. Rebuilt it several times with LP or HP pistons, and latest somewhere back in May this year I don't remember what I did, but the lower horizontal tube is cold when working, also need extra time about an hour to reach the pressure from 200 to 300 bars on a 14L tank. But the lower tube I can hold in my palm. I was busy lately and still enough air in my 3 tanks, but I know I will need to open it again next time in my hands.
 
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Mine is over 6 years old. First time it started losing pressure I tried just replacing the upper cylinder rings with the rings that came with it. That lasted a little while then it started not building pressure all the way again. Next time I just replaced the whole upper assembly that I got through Ali express. I did have trouble with the lines leaking after the both rebuilds. I removed the lines and sealed them with some Permatech aviation sealer. That fixed the air line leaks. Mine has been good since. That was 3 years ago. It does run a little hotter then when it was new. I typically see 65c on longer runs.
 
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bigHUN said:
I have mine for 4 years, totalling about 65 hrs. Rebuilt it several times with LP or HP pistons, and latest somewhere back in May this year I don't remember what I did, but the lower horizontal tube is cold when working, also need extra time about an hour to reach the pressure from 200 to 300 bars on a 14L tank. But the lower tube I can hold in my palm. I was busy lately and still enough air in my 3 tanks, but I know I will need to open it again next time in my hands.
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I'm tearing into it again in the next day or so. Trying everything I can think of with the spare parts on hand. We'll see where this leads. I would love it if I can get it running right. Hate to think I've been "beaten" by a Yong Heng! BTW, in the years of service my YH has never gone above 45 degrees Celsius
(114 F.)
 
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Gerry52 said:
I totally forgot I bought a 4 year warranty when I purchased the YH! Anybody on the forum have experience with warranty & return? How'd that work for you?
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Depends where you bought it. Mine was through Walmart. When it failed, walmart said the seller is responsible for the first year.After a big hassel, walmart refunded my money,voided the warranty and told me to keep the unit., the gauge was leaking.
 
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bckyrdsnpr52 said:
Depends where you bought it. Mine was through Walmart. When it failed, walmart said the seller is responsible for the first year.After a big hassel, walmart refunded my money,voided the warranty and told me to keep the unit., the gauge was leaking.
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You scored! Got mine thru Amazon. Really don't think the warranty thing will pan out.
 
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