SonexBuilders.net

Greetings...

- 3300A s.n. 1053, upgraded lifters and pushrods

As part of my pre-flight, I hand prop the engine through all cylinders. Yesterday, I heard a 'clanking' noise, so I went around again. I heard the same noise at the same location, so I investigated further. Seems it's just before TDC on cylinder 6, and can be reproduced just by rocking the prop back and forth.

https://drive.google.com/open?id=1AKVFA ... 4xKfw9eWBA

As seen in the linked video (can't seem to attach it) , the noise only occurs when there is compression, disappearing when spark plug hole is open. It's quite a loud 'clank', and takes very little prop movement to repeat ad infinitum. Note that both valves are closed and there is no discernable movement of either rocker, which would seemingly eliminate the valve train a suspect.

Any ideas?

Sure sounds like this:

https://www.youtube.com/watch?v=9CkSQR2HTek



Rick
Sonex 524

Thanks, Rick, pretty sure that's what's going on here. removed the #6 head yesterday, there's a lot of 'rock' in that piston:

https://drive.google.com/open?id=1XmuWp ... 5jpGOBSDag

Little-to-no scoring or scuffing in the cylinder, at least to my untrained eye, so Im not sure Pete's 'cold seizure' theory is applicable in this case. Which begs the question why there is so much 'rock' and subsequent slap. Looks like i'm going to be replacing the piston, however. Sure would like to know the cause. To prevent it from just happening again (or happening to other pistons). I'm totally anal about warming the engine to 100* F, got my E.I.S. set to that. And I pre-heat religiously in colder ambient temps. Hoping that Pete will chime in soon...

Hi guy,
Not sure , because never had our jab3300 apart, but some pistons have an offset wristpin for the powerstroke. Is it possible that the piston is 180* out of position? Maybe some wear and finally piston slap. Whats the history of that engine/cylinder? Has it been apart before? Was it installed incorrect at factory? Or later had maint. on that cylinder ? . Was goood you observed this and taking steps to correct before further flight. A call to jabiriu usa is in order, hopefully you remember the orientation of the piston as you disassembled it. Good luck and let us know.

WaiexN143NM
Michael

Hi guy,
What was your outcome of this problem?
Thanks!

WaiexN143NM
Michael

He posted some pics via the JabCamit yahoo group..

https://drive.google.com/drive/folders/0B0eD0uA4Gw3nQnN3RWlkeHI0c2c?usp=sharing

Broken piston skirt. See complete thread over at the JabCamit yahoo group. I wasn't getting much feedback on this group...
link to pics: https://drive.google.com/drive/folders/0B0eD0uA4Gw3nQnN3RWlkeHI0c2c?usp=sharing

J.

Hi ,
Thanks for posting the pics. The next question is how did this happen? And the metal that fell into crankcase, ? , now what a complete teardown? Good luck! Keep us jab owners in the loop. Prob not much feedback here because nobodys had this happen to them . Any others report anything like this in the other groups?

WaiexN143NM
Michael1

Well that's not good. Hopefully it happened just as you shut it down last time and will reduce the parts count on a rebuild.

Don't know when or why it happened. Shipping engine to JabiruNA for rebuild :(