Mr. Yongs gettin a death rattle

I bought a whole rod and piston assembly for mine. I've only seen most parts available thru ali express or the like. I made some questionable modifications to the first replacement I put in. Which resulted in a quick failure again but was worth testing. Waiting for the 3rd one to show up. (#1 lasted a year with hard use) 

I do know there are two rod types. 85 and 89. Which are clearly marked on the rod in large figures. These have different length lengths.

My auto shut off Yong Heng is over 2 years old. Noticed lately it’s getting a pretty good rattling sound to it. Any advice on where to order parts and what parts to order. Would like to rebuild it before it goes catastrophic. I know some of you guys have been all through these things so that’s why I’m asking. I don’t want to waste time and money by ordering the wrong parts. If it’s like Chinese mini bikes, you have to order 3 sets of brakes to find one that fits the bike that was made on Tuesday.

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May sound silly but sounds like somethings rattling itself loose may be worth cinching things all up before getting overly panicked about it. Yo!

More silly questions When was it's last oil change how's the oil level? Too bad you can't use something like BG MOA in it. Yo!

My guess is that the high-side piston is broken. See https://www.airgunnation.com/topic/yong-heng-second-stage-piston-breaking-not-any-more/

Just replace the broken piston. make sure that it's a Yong Heng and it's the new version. use high-temperature-high-strength Loctite on the thread of the piston head and the screw connecting it to the first-stage piston

I would have to agree with airgunfans

My YH has rattled badly twice. The first time is when it was nearly new and the second stage piston had no lock tight applied, at the factory, so it came loose and destroyed itself. So, I got a new piston $12 from aliexpress and once installed it knocked again. Not because I forgot to put oil in it, which I did, but because the piston was to long. I filed a few thousands off of it, filled it with oil and it has been filling my tanks and guns for a couple of months now.

https://www.airgunnation.com/topic/a-tale-of-two-yong-hengs/

If you caught it soon enough you may be able to just pull it clean up the threads and reinstall it although at two years old I would probly do the rings also. The top two rings unscrew from the rest and this allows you to carefully stretch the new rings over and into their slots.

I think that it's better to order the whole piston, rod assembly. It's about $25. about the same price as just the small piston by its self. If it was the top of the high-pressure piston separating, it would have destroyed its self by now. I've heard of them starting to rattle when the low-pressure piston is starting to fail as well. The newer ones have a beefed-up crown. I got one for a spare 18 months ago and it was the stronger version. I haven't needed it yet. When ordering, make sure it's for a YH. The longer ones are for the Tuxing branded models. They can be distinguished by the four ring-lands as opposed to the YH's three. Here is somewhere to start. https://www.aliexpress.com/item/33000794368.html?spm=a2g0o.detail.1000014.21.61735cbcKSoRE2&gps-id=pcDetailBottomMoreOtherSeller&scm=1007.14976.158757.0&scm_id=1007.14976.158757.0&scm-url=1007.14976.158757.0&pvid=ee4fd1cf-a4e4-400f-95e3-f3066c522ef5&_t=gps-idcDetailBottomMoreOtherSeller,scm-url:1007.14976.158757.0,pvid:ee4fd1cf-a4e4-400f-95e3-f3066c522ef5,tpp_buckets:668%230%23131923%2311_668%23808%235965%23492_668%23888%233325%2313_4976%230%23158757%230_4976%232711%237538%23679_668%232846%238113%23645_668%232717%237560%23266 These are preassembled. Just pull the top off and swap it out. You won't even have to drain the oil or remove the front cover. The only gasket that you may need is the cylinder base gasket. I got mine from the same supplier. If you are feeling flush, you might want a whole new top-end. Try this for well under $100 https://www.aliexpress.com/item/32789051687.html?spm=a2g0o.detail.1000014.5.77b35cbcUoXw0p&gps-id=pcDetailBottomMoreOtherSeller&scm=1007.14976.158757.0&scm_id=1007.14976.158757.0&scm-url=1007.14976.158757.0&pvid=ef677402-776e-43a9-8455-f01cdff91c21&_t=gps-idcDetailBottomMoreOtherSeller,scm-url:1007.14976.158757.0,pvid:ef677402-776e-43a9-8455-f01cdff91c21,tpp_buckets:668%230%23131923%234_668%23808%235965%23492_668%23888%233325%2313_4976%230%23158757%230_4976%232711%237538%23679_668%232846%238113%23645_668%232717%237560%23266 If it was me, I would be pulling it down before ordering anything or before it tosses a leg out of bed. You'll have a better idea of what you require or even if it is worth fixing before throwing good money after bad.

I have read some folk suggest buying a new unit, and using the old for parts, however reading above it may be that any "new unit" could have different parts.

good luck.

I have read some folk suggest buying a new unit, and using the old for parts, however reading above it may be that any "new unit" could have different parts.

good luck.

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Base on the reports here, only a handful of parts are prone to breakdown so there is no point to buy another unit just for the spare parts. My recollection : 

- pistons ( 1st and 2nd stage )

- connecting rods

- relay

- reed valves

- O-rings, seals , piston rings

- pressure gauge

I bought my spare piston and gaskets/reed valve from The Yong Heng Store on Aliexpress: https://www.aliexpress.com/store/2940062?spm=a2g0o.productlist.0.0.4fe4b076wNDfSb

I'm still waiting for the order to arrive. Lots of wait time for stuff from China due to the pandemic.

Mine had a rattle for a long time before the rod broke. There's no end cap, it just slides snug on the end of the crank. My 2nd stage piston never was loose. But the design inherently side loads the rod. You'll see whwen you take it apart. I tried to alleviate that some, but the rod couldn't hold up. It seems it's structure barely withstands the load it's under.



Complete rod, piston(s) rings, wrist pin, and snap rings assembled is $20 shipped. No reason to just get a piston, get the whole thing. 

Hold on folks! This might not be a piston issue at all. The Yong heng has a ton of vibration when it's running correctly. Inside the compression chamber is a filter. Mine fell out because they don't use any teflon tape or pipe dope during assembly. It caused a horrible rattle that would stop occurring sometimes. Only way to know is to take it apart and look. Do yourself a favor and order some new crush seals and bolts now from Ali express. Sometimes they won't seal a second time after disassembly. Good luck

Also good advice on crush seals. I had to use Alphabet org to get mine to soften. The heat makes them hard as rocks!



I was under the impression the filter was the gold thimble looking thing and is external.



Either way, keep us updated if you don't mind