Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

To me the more serious issue is the piston pins not being retained by anything!
The piston pins will move during running and ultimately score the cylinder walls and reduce the compression while putting loose metal pieces in the engine!
There is a video on YouTube of the H73 (single cylinder version) disassembled. This video shows the piston pin without any form of retainers. The video shows making retainers by cutting a small piece of O ring and placing it on each side of the piston pin.
This is a quick and clever way to fix this issue. I was thinking of making a small Teflon button to go on each side of the piston pin like what is done on racing engines sometimes.
 I’m a Machinist and own a Lathe and Mill and have at lot of knowledge about engines and racing but many buyers will be stuck with the current Chinese design oversight and Quality issues.
 It’s still a great deal but it’s best to know all the flaws before running it too much.