RE: bubbles in OS 50 sx
I have two .50 SX and both had the same problem: bubbles between needle valve and carb. No bubbles at all were detected between the tank line and the needle valve.
Sent one to OS for warranty repair. When it came back the piston, cylinder liner and both ball bearings were changed at no cost and it runs like magic. No more bubbles...
Warranty is 2 years with invoice...