u/TheHighDwarf420

Hey guys, I’m losing my mind with Honda GX390 rebuilds and hoping somebody here has ideas. I currently have 5 GX390 engines. The weird thing is the FIRST engine we rebuilt smoked like crazy at first, then we rebuilt it AGAIN without really changing anything important, and suddenly it worked perfectly fine. Now the next TWO engines I rebuilt are smoking badly again. What was done:

• New piston rings installed
• Cylinder was NOT honed afterwards
• Cylinder walls are not mirror smooth, still have some texture
• Head was shaved to second oversize specification Symptoms:
• Massive smoke from exhaust
• Engines use oil quickly
• Compression feels strong/good
• Engines run otherwise normal
• No oil coming out of oil refill hole
• No oil inside carb
• No oil inside breather tube from valve cover to air filter I also tried running them for a while hoping the rings would seat, but they still smoke heavily. About the oil rings:
• Oil ring gap/clearance seemed okay
• But the oil ring expander tension felt pretty weak / low tension What confuses me:
• First engine smoked horribly after rebuild
• Rebuilt it again touching almost nothing
• Then it became completely fine
• Next two engines built basically the same way are smoking badly

Any help appreciated because this is driving me insane.