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So I picked this engine up to replace my prop strike engine.. it wasn't cheap.. have this noise when I pull the prop through by hand. When I pulled the plugs on the cylinder the noise goes away. To me it sounds like maybe piston slap? The engine is smooth and runs great! Does anyone else have this noise? 200 hours snew.. not looking forward to overhaul...

https://youtu.be/wZvEY0WpXFc

I’m no expert as to the source of that sound, but my Jabiru 3300 definitely does not make that noise.....

Sounds like this....

https://www.youtube.com/watch?v=22z4HvFkfbc

Does it make the noise both hot and cold? On each cylinder? At TDC or other stroke? In normal rotation direction of both 'backwards' and normal?
It sort of sounds like a sticking valve stem that is letting the valve 'snap' shut on it's seat. Narrow it down to which cylinder (or all), which stroke, hot or cold, etc. That will help guide you to the EXACT time and place of the occurance.

Joe Gibson

I agree, it doesn't sound nice! I'd vote to take the rocker covers off and watch the valves and rocker gear. It does sound like a valve snapping shut. Good luck. I've got a 2200, they are easy to work on and spare parts aren't too scary.

IF it's an exhaust valve hanging up slightly in the guide, it's not the end of the world.
When the guide gets a little wear, it allows exhaust gasses to pass through the stem rather than out the valve head itself. Those hot gasses 'coke' up deposits on the stem and guide.
IF it's that, first try spraying a little carb cleaner or other gum cutter on the valve stem and workin the valve by turning the motor over back and forth by hand. (That's one of the reasons rocker arms have a 'toe' so that the valve is always rotating slightly when running.)
IF that's what's going on, usually when the motor is hot it disappears as everything comes up to normal temperature and size. BUT if left to it's own devices and the valve isn't cleaning itself, it may eventually stick open altogether rendering that jug dead.
IF that doesn't fix the sticking, it's not a big deal to drop the valve into the cylinder (the old rope trick) and SLIGHTLY ream the deposit out of the guide.
Investigate it carefully to narrow down the cylinder and exact issue.
Just a suggestion.

Joe Gibson

Please keep us posted on what you find.

Joe Gibson

It's not good. Pulled 5 and 6 heads and the pistons rock back and forth in the bore. This replicates the sound. I'm working on pulling the jugs to see what the damage is. Either way fixing wont be cheap. At the minimum looking at a Hone, new rings and pistons. Not happy. I paid alot of money for this and feel like the guy who sold me the engine knew. And I sold my prop strike engine so I cant even move the cylinders over.

Jugs pulled. Cylinders on left side are fine, but piston skirts are trashed. Super scuffed up. No wonder it rocked back and forth.

That buy was bad luck. This overhaul service bulletin just came out a couple of months ago and is probably quite relevant. https://jabiru.net.au/wp-content/upload ... Issues.pdf
If your engine only has single valve springs it might be a good time for you to upgrade to dual springs.
Steve
Sonex 892