G'day Digger,

I have seen the issue of excess oil from the muffler stop an engine on the second or third flight. In this case it was an older OS 46 SF. The muffler nipple was flush with the inside of the muffler and was allowing raw oil to travel to the tank. It took us months to work it out, but eventually we mounted the engine and tank on a stand. When we ran it we could see the raw oil droplets accumulate on the bottom of the tank. Eventually the clunk would pick up a slug of raw oil and the engine would die.

The fix was to fit a longer nipple.

I remember Brian Winch mentioning a similar problem in Airborne Mag. Turned out to be a home made rubber or similar exhaust extension. The extension would be fine for the first flight but would heat soak and slowly soften. By the second flight it would collapse and either strangle the engine or change the pressure to the tank enough for the engine to die. Of course by the next weekend it regained its strength and the process would be repeated.

Can't quite see how this would affect all your friends engines but hope this is some help

Good luck

Dave H