I have come across about 4 such reports in this forum and these are three of them :
https://www.airgunnation.com/topic/dang-yong-heng/
https://www.airgunnation.com/topic/yong-heng-8/
https://www.airgunnation.com/topic/death-of-my-yong-heng/
The following photos are from these threads showing how the piston broke :
Today I took this to the Yong Heng factory in China and they told me that they are aware of the problem and have subsequently done some enhancement to the piston including :
They told me that there have not been any more reports about such failure over the last few months. It seems that the new piston was out not too long ago.
I have ordered the new piston + rings which costs 35 Chinese Yuan or 5 US$ shipped to Hong Kong. Expect to arrive in about 4 days. Will report more details later.
Update Oct 10th :
OK, finally got time to take out the old piston from my Yong Heng and do a side-by-side comparison. With the rings installed, there is no visible difference. The upper one in the photo is the old version, the new version is beneath it :
However, after removing the top ring, a major difference can be seen at the root of the top disc. There is a fillet making the root 25 ~ 30% thicker. They told me that the brass used in the new version is of better quality as well. Hopefully this will solve the problem for good.
https://www.airgunnation.com/topic/dang-yong-heng/
https://www.airgunnation.com/topic/yong-heng-8/
https://www.airgunnation.com/topic/death-of-my-yong-heng/
The following photos are from these threads showing how the piston broke :
Today I took this to the Yong Heng factory in China and they told me that they are aware of the problem and have subsequently done some enhancement to the piston including :
- Better material
- Adjustment of some dimensions
- Changing the cross section of the spacer between rings from “T shape” to “Y shape” . I believe that means thickening the root where the breaking occurs as shown in the photos above.
They told me that there have not been any more reports about such failure over the last few months. It seems that the new piston was out not too long ago.
I have ordered the new piston + rings which costs 35 Chinese Yuan or 5 US$ shipped to Hong Kong. Expect to arrive in about 4 days. Will report more details later.
Update Oct 10th :
OK, finally got time to take out the old piston from my Yong Heng and do a side-by-side comparison. With the rings installed, there is no visible difference. The upper one in the photo is the old version, the new version is beneath it :
However, after removing the top ring, a major difference can be seen at the root of the top disc. There is a fillet making the root 25 ~ 30% thicker. They told me that the brass used in the new version is of better quality as well. Hopefully this will solve the problem for good.
