064 big bore exoloded on startup

[RED-85-Z51]

Customer brought me a toasted 064 he wanted rebuilt, ive done a few with 066 kits with little issue, this one though, had a ton of compression after i got it together, i had hopes it would loosen up as any assembly lube burned off. I got it to start, it idled for about 10 seconds, i goosed the throttle and bang... The whole cylinder blew off, piston exploded, wrist pin went 25 feet across the shop.

I found the bearing, plug boot, rod wasnt broke and no case damage beyond all 4 bolts pulled completely out of the case.

I ordered another kit, 2 base gaskets, a tap, drill bit, and 4 longer, larger allen head bolts. Drilled the block out, tapped the holes, put it all back together and it ran good, not gonna lie the first time i took it to the limit, i closed my eyes and looked away[emoji1787].

I guess an extra gasket, and longer larger bolts were what it needed,. Its a break even job.. no wonder no other shop in town would touch it.. but i now have the know-how and experience, and tools to make larger holes for cylinder head bolts on that platform of Stihl saw so thats a win.

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[Jkstihl]

I have never seen a chainsaw blow it's dome lol....that was brutal.

 

[L34]

Piston hit head??

 

[RED-85-Z51]

Appears the cylinder blew off and let the piston come out partially and smack the block. But there was no contact, no crown contact at all.

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[Bob Hedgecutter]

So, I guess no soft solder was harmed after the initial build up, before the initial fire up?
As we say over here..... BUGGER!

 

[L34]

Big bore above 064 as in 066 or big bore 066?

 

[L34]

Was the original threads compromised in any way,m5 bolts I assume.

 

[L34]

If 066 BB did piston skirt hit crank weights?

 

[RED-85-Z51]

O64 big bored up to an 066 top end, i think iy was 2mm larger bore, it did Clear the bottom end.

Stock bolts were M5, i went to M6x1. 0 and made some minor clearancing for the roughly 4mm longer bolts to be inserted.

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[Jkstihl]

Well something made contact, there's no way around that....somebody's saw didn't get mic'd when they were finished.

 

[RED-85-Z51]

If i still had the top end id show you, but there was no contact at all with the crown, and the piston wasn't stuck, There was ample clearance between the skirt and the block, and skirt to crank. Didnt have any knocks or rattles, i spun it up with the compression release plug removed with a drill and there was 0 contact. It probably had 220psi of compression... It was nuts.

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[Jkstihl]

Maybe piston broke at wrist pin boss at rpm?

 

[RED-85-Z51]

Maybe piston broke at wrist pin boss at rpm?

Always possible, but it was only at maybe 4500. First blip of the throttle... Done.

I can only surmise tolerance stacking, squish too tight, thin gasket... Maybe the threads were weak, but they held Torque fine.

I know if the muffler hadn't hit the loop id have eaten the cylinder

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[Jkstihl]

Always possible, but it was only at maybe 4500. First blip of the throttle... Done.

I can only surmise tolerance stacking, squish too tight, thin gasket... Maybe the threads were weak, but they held Torque fine.

I know if the muffler hadn't hit the loop id have eaten the cylinder

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That's crazy!.. and by the way I noticed you posting from a LG g8 how you liking yours? Love mine so far! Paid 169$ shipped on eBay for a mint condition unlocked one..it's truly one of the best phones out right now and to be able to get it at that price is unbelievable.

 

[RED-85-Z51]

Ive had this one since June of last year, my 2 year old G5 dropped screen down and the g8 was available, I paid a painfully larger amount for it back then. It works okay, its never blown me away, the camera is very mediocre, memory is good, battery life is great, screen is good, speaker is okay but gets distorted at higher volumes. Im starting to get some operating system glitches, freezes... But, so far no boot loop or self restarts. LG has abandoned the flagship G series unfortunately

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[Bob Hedgecutter]

Always possible, but it was only at maybe 4500. First blip of the throttle... Done.

I can only surmise tolerance stacking, squish too tight, thin gasket... Maybe the threads were weak, but they held Torque fine.

I know if the muffler hadn't hit the loop id have eaten the cylinder

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Yeah- na, sorry, I am not seeing 220 psi tearing the entire cylinder off the case, tearing out all four supposed good cylinder bolts and grenading the piston without some form of mechanical help from the crank.
Guessing the kit was from the red flagged nation?

 

[Jkstihl]

Ive had this one since June of last year, my 2 year old G5 dropped screen down and the g8 was available, I paid a painfully larger amount for it back then. It works okay, its never blown me away, the camera is very mediocre, memory is good, battery life is great, screen is good, speaker is okay but gets distorted at higher volumes. Im starting to get some operating system glitches, freezes... But, so far no boot loop or self restarts. LG has abandoned the flagship G series unfortunately

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Are you on Android 10? I came from the v20 and the g8 literally blows me away. Weird you don't like yours, if you updated to Android 10 did you do a factory reset after updating? Camera is just as good if not slightly better than wife's iPhone xs, only cons I have found so far is sound quality while recording loud objects(like chainsaws) tend to have a tinny type distortion, as far as sound playback it's on par with iPhone xs, slight louder also. Processing power is top shelf. Battery life is great like you said.

 

[RED-85-Z51]

Oh yes running 10, that changeover was a disaster. Phone shut itself off on the restart and bricked for 30 minutes, wouldn't do anything. Then... With no warning, self restarted. They changed the keyboard somehow also and ive fought that too

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[Jkstihl]

Oh yes running 10, that changeover was a disaster. Phone shut itself off on the restart and bricked for 30 minutes, wouldn't do anything. Then... With no warning, self restarted. They changed the keyboard somehow also and ive fought that too

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Settings-system-language&keyboard-default and select Gboard that's the better keyboard over the lg keyboard. Any other issues id be glad to help

 

[trains]

Hard to tell from the pictures, but it looks like casting flaw where the journal web meets the crown base of the piston, and it failed and the momentum from the crank was enough to push the jug off once all the bits became spare parts in the crank area, very clean even break along a semi flat area, my money is on poor casting from china stuff.

The only thing china got right was the cov-19 virus, its worked better and lasted longer than any other junk they make.