Yong Heng piston cracking - no more ! ( hopefully )

[airgunfans]

There has been quite many reports on the top of the first-stage piston of Yong Heng cracking after some use. Although mine has been working fine for about a year, I decided to take this to the Yong Heng factory in China and see if they will do something about it. It turns out that they have been listening to you guys quietly and have made a strengthened version. The new version costs about 4 bucks shipped to Hong Kong. The package includes the piston with rings, retaining rings for the wrist pin and a pair of gasket for the first-stage cylinder. 

left : old version, right : new version

The measured thickness of the top is 2.75 mm for the old version and 4.38 mm for the new one which represents a good 60% increase in thickness. They told me that all compressors coming out from the factory now are equipped with the new piston. If you guys need to replace the piston, make sure that the new version will be ordered. 

left : old version right : new version, note the big difference in the thickness of the top

The most visible differences are on the inner side : 

 

[boscoebrea]

Great news,is there a way to tell the new model from the old model.

 

[DirtyDovi]

Very cool!

I've read about these new / improved piston, ring, and seal kits a few times, 
but this is the first time I've gotten to see a side-by-side comparison.. Thanks for the heads up! 

The new version most definitely looks like it's going to eliminate / fix any of the previously known problems. 

 

Sam -

 

[Brian10956]

Lust look at the last picture in the hole in the center you can see it’s thicker 4.38mm if you measure it.

 

[edosan]

I can see the difference! nice! thanks for sharing

 

[DesertSilver]

So the piston is cracking on the crown of the piston?

 

[Joer]

The big problem is finding one of these new pistons in the marketplace. It would have been nice of them to provide the name of a vendor on AliExpress that carries them.

 

[DirtyDovi]

So the piston is cracking on the crown of the piston?

On the top of the piston, where the high-pressure connecting rod joins,
people were experiencing damage/failures when the metal would either cave in, crack, or ovalize... 

At first, it was thought the issue was due to the compressors going high pressure hard-stops.. 
Others reported only doing soft starts and soft stops [bleeding pressures before turning on/off]
but still experiencing damage.. 

The new design [added wall thickness] should really help with that!

 

Sam -

 

[edosan]

The usual problem, should be fixed with the new piston

 

[Tweeter]

I plan to buy a Yong Heng when (if) my Vevor ever quits. Do you know if there will be any way to tell whether or not you're buying a Yong Heng with the new piston? Probably just order a new style piston at the same time to be sure... This is good news though, thanks!

 

[Eaglebeak]

I have a new piston and rod assembly on order, from Joto as a backup, just in case mine fails. I am assuming that it will be old stock. I have noticed that the official Yong Heng AliExpress site, no longer lists spare parts. It will be interesting when these become available, who will be on selling them and whether they will be able to be bought separately or as a kit with rod and gudgeon pin, as is the case now. I doubt that the makers will appreciate having to deal directly with the public, especially when at $4.00 per unit shipped there is no profit in it and a probable loss. Keep us posted if you learn anything more about these details. 

 

[Eaglebeak]

My new rod and piston arrived today. After measuring the new piston, it appears that I have the new thicker crown type. The $22 USD price ended up converting to $45 AUD with shipping, tax and gaskets. Still worth every cent for having a quick fix, just in case mine drops its lunch.

 

[Joer]

My new rod and piston arrived today. After measuring the new piston, it appears that I have the new thicker crown type. The $22 USD price ended up converting to $45 AUD with shipping, tax and gaskets. Still worth every cent for having a quick fix, just in case mine drops its lunch.

Thanks for providing the feedback on the new piston. My Yong Heng was made the end of 2018 so I am hoping it has the new piston.