Death of a big bore 372

[tickbitintn]

This BB kit is at least three or four years old....
I ran a few gallons thru it before it spent a little time on the shelf... duties taken by a 576....
Then traded out for some tree work ( a heavy leaner over my house).
They flogged the daylights out if it for just shy of a year.
Passed vac/leak test...
Single tang circlips intact and in place...
Intake tract clean...
Any guesses on the cause of this failure??

Edit: first two pics portion of lower ring is removed but was there upon jug removal, and is in place for ex and side pic.

 

[tickbitintn]

Forgot to mention all bearings in bottom end (crank,rod and pin)are all intact and show no signs of wear/damage.

Sent from my XT1254 using Tapatalk

 

[Onan18]

Looks to all the world like it are something, ring locating pin?

 

[jimmorrison]

Spark plug electrode?

 

[2manyhounds]

What's missing in the carb?

 

[tickbitintn]

Pins intact.
It had a new ngk plug installed when I got it... So I can't say on a plug failure but it had a ngk in it when it left me...
I had not looked in the carb yet...

Sent from my XT1254 using Tapatalk

 

[Fullkip]

Looks like it ate a piece of the ring... Was this an after market kit?

Fullskip

 

[2manyhounds]

Seen a busted air filter/cover screw do something very similar on a 200t

 

[huskyboy]

Chrome came off cylinder bad? Rings worn enough to catch a port from too much play? Mines been strong 2 years now and I've beaten the living piss out of it tuned to 14k rpm. We'll see if it continues to do so.

 

[XP_Slinger]

Looks like the lower ring let go right at the gap when it snagged the exhaust. By the shape of the damage on the piston I can't think of what else it could've been. Man that's a shame.

Side note: I thought by the title of your thread Husqvarna was no longer gonna be making 75cc kits. I was like "no frigin way! Dammit!" Thought my 75cc plans for my 372 X-Torq were done...lol

 

[tickbitintn]

Bottom ring failure is all I could think of... Machine marks can still be seen on the piston... muffler was full of ring bits...
Too bad was a good runner...

Sent from my XT1254 using Tapatalk

 

[BuckthornBonnie]

Bottom ring failure is all I could think of... Machine marks can still be seen on the piston... muffler was full of ring bits...
Too bad was a good runner...

Sent from my XT1254 using Tapatalk

Yikes.