Yong Heng Failed Today

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heavy-impact

heavy-impact

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Sep 13, 2018
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Right Coast, USA
My yong heng failed today, made a few knocking sounds and then started losing all the air around the back of the head somewhere.

May just be a gasket. I have a piston and rod but no gaskets.

I could measure the gasket thickness and buy a sheet of gasket material to cut them out of (cnc laser) but I'd rather buy them ready to go.

What's the quickest source for parts?

Please share your experience rebuilding one of these compressors.

Thanks

James
 
Quickest ought to be any seller stateside. I'd check amazon and ebay. But markeup is pretty steep.

Now, I have ordered stateside and had it ship from china. And I've ordered from china, and have it ship out of New Jersey. So, not a %100 strategy to get the part in a timely fashion. But highly probable.

I just bite the bullet and order from ali express. Seems they also have the best selection of parts over there. Just make sure to measure your connecting rod if you're ordering one. Journal to journal, will be either 87 or 89mm. Also, I know you won't, but dont be an idiot like me and do a crank case to cylinder head gasket delete. Only attempt if you want a bent crankshaft. So, make sure you get the FACTORY gaskets. Piston to head clearnace is a real thing! Also recommend a grade 12.9 LH M8x1.0x25mm bolt for crankshaft. Not easy to find, but find them I did on ali, lol.


 
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Parts from eBay will be faster than overseas, but what is the problem? There's a dowdy seal on each of the three pipes, one on each end. Those blow constantly on mine. Your spare parts kit that came with it should have a couple spares. You can buy more stateside if you need.

I blew the top piston. The compressor simply locked up, so that doesn't seem to be your problem. I had new piston tops (the top of the piston screws in, so I just ordered that part) and replaced it. There are videos on YouTube showing all the steps, but TAKE PICTURES OF THE REED VALVE. I downloaded the only video I could find on how to put it back together. https://www.youtube.com/watch?v=24sGXYkd4NY

The worst part is that it took two months for the top of the piston to show up, then when I tried to reassemble it, the gasket had shrunk and I had to order another oil gasket and was down for another 2 months. If you need to remove the front of the compressor, might want to just order another gasket unless you are good at making your own.

If it's just a seal, you can start the compressor, let it build a little pressure. Hold your hand to the sides of each of the metal pipes. If you can feel air escaping, it's probably one of those dowdy seals. I've replaced so many, I've got a system down. Though remember the metal pipes screw into aluminum blocks and are easily stripped. Use two open end wrenches to tighten the pipes on top of the dowdy seals.

And of course, if the repair will be over $75 or $100, just buy a new one and keep the old one for parts.

Good luck, they are very simple devices, but a real pain to work on.
 
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I had the opposite problem with the front seal. Mine was too oil saturated and was too big to shove back in place. I used regular old clear silicone sealant for the front crank case cover. I've since pulled the front cover off many times and never needed to add more silicone or re-do the original job.

If memory serves... part of the front seal/gasket keeps oil from being splashed up at the breather.... I had to gut a lot of the breather baffles because the tight clearance in them was picking oil up (that was being splashed up) and pushing it out. 
 
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honestly i wouldnt at the price point theyre at .. i could see learning off the dead one and using it for parts at a future date, but i kbow how these things go .. it goes from dead to a turd you spend double what a new one costs trying to fix to buying another one anyway lol ...
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I've got $30 in a piston kit and there's a good chance it's only a dowdy seal like Saltlake58 mentioned. I just need to go out to the shop and assess it. When it gave trouble I just turned it off and went in the house. If I need paper gaskets I can cut them on the cnc laser, I just need to know the proper thickness.
 
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Sounds like you lost compression on primary piston or an issue with the check valve. Valve is inside the outlet of cylinder 1. Also will recommend lapping compound if you have any issues getting hard line seals to hold seal after reassembly. 

Top cylinder head is just orings so you can pull it and check clearance if you need. On the chance you don't get a gasket measurement I'd try 2 and 3mm 
 
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I have the measurements you requested. First stage cylinder to crankcase gasket is 1.25mm. First stage head gasket is 1mm.

Be careful with the second stage piston to head clearance. After I replaced the top part of my second stage piston I could hear it whacking on the top of the head. So I tore it down again and sanded a couple three thousandths off of the top of it. That was all it took and it was good to go. Running for better than a year now after the repair to the newly new unit.
 
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Does anyone know how many hours of run time does one achieve under normal operation before a YH compressor needs to be rebuilt?



I have thirty on mine thusfar.
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Do you have the link for the best Yong Heng vendor on aliexpress ?



Thanks!



Shipping prices have skyrocketed lately so eBay and Amazon usually have better deals on the YH these days.
Click to expand...


 
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I have over 30Hrs in year and a half.

Last week I changed the oil (a second time in total), but my mistake was not checking how much oil I had in my hands........I went to couple stores nobody had just any compressor oil and amazon was late for one week. so I knew I had not enough oil and run it almost dry for over half an hour, basically I bake it because I wanted to top up my tank and go shooting...I was gambling with YH and that was a price, The piston rod seized. I had spare parts already in house and ones the amazon oil (royal purple) arrived I refreshed the YH in no time. No other problem all the 30 Hrs total run time.
 
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I have over 30Hrs in year and a half.

Last week I changed the oil (a second time in total), but my mistake was not checking how much oil I had in my hands........I went to couple stores nobody had just any compressor oil and amazon was late for one week. so I knew I had not enough oil and run it almost dry for over half an hour, basically I bake it because I wanted to top up my tank and go shooting...I was gambling with YH and that was a price, The piston rod seized. I had spare parts already in house and ones the amazon oil (royal purple) arrived I refreshed the YH in no time. No other problem all the 30 Hrs total run time.
Click to expand...

Always have some oil at hand. Go to Harbor freight and grab some of their compressor oil and never have this problem again, at 1/3rd of the price it works just as well and it's clear so you can gauge how dirty it is in use with your own eyes.
 
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I just got around to pulling the cylinder off and just as suspected the top of the primary piston is caved in and there appears to be evidence of detonation on the secondary piston. There are two little balls of brass in there and half of the brass piston surface is missing. I had Royal Purple compressor oil in it. I'm waiting on the penetrating oil to soak in on the head bolts but when I get that off and inspect the valve body I'll know more.

Disassembly is very easy and there is no need to remove the crankcase cover unless you need to clean inside there. I should have an update soon.
 
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Disassembly is complete and all other parts were in like new condition. The rings on the secondary piston (the brass one) seem to be a graphite material and had a lot of wear on them. The graphite and oil paste was all over the brass piston under the rings but this may be normal. There's no way to know if detonation occurred before the piston collapsed and caused the piston failure or after as a result of the oil getting by. The original connection rod is still like new.

My unit was an earlier model which had thinner primary piston tops (the aluminum one). The manufacturer told me that they were making the primary piston thicker on top to help remedy this problem. I ordered my piston/rod assembly over a year ago and specified that it must be the new thicker style. After measuring the old and new piston the top of the new one seems to be about 1mm thicker.

Now I have to order paper gasket material to cut the new gaskets from and then I should be up and running again. I'll make a top end rebuild guide after I'm done to help those that are not comfortable diving in on their own. There are youtube videos but it's like two hours of the guy's random thoughts to find five minutes of information.

It would be nice if someone in the USA would stock parts for these pumps. If you had all the parts the whole job could be done in less than an hour so I think these pumps are still the best deal out there by a wide margin.
 
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