Briggs & Stratton Crank

[Luffydog]

Could hear some noise going on but hard to tell just what was going on. Might be the piston kinda hard to tell from the video. I have Kohler engine I have to breakdown for a warranty. Kohler wants me to give them the reason why it failed. Sometimes u have to learn where it failed before u can fix it and learn why it failed and to determine if it can be fixed without another failure. If cost is up near a new push might be better off to condemn it and tell the customer that u rather see the money spent toward a new one that he might be better off. Good luck on the learning and expect some curves to be throwed at u more than one direction of travel and at different speeds.

[Fulltilt]

Ah, yes, the saga continues......

Sounds like you have pin/keeper problem or maybe broken rings. May have been improperly installed ( upside down, wrong groove, etc) dunno. Did you check the ring end gap before you installed them? Was the piston on the rod correctly( some are offset ) was the clip fully seated? Did you forget to install one of them altogether?

[lefty]

Ah, yes, the saga continues......

Sounds like you have pin/keeper problem or maybe broken rings. May have been improperly installed ( upside down, wrong groove, etc) dunno. Did you check the ring end gap before you installed them? Was the piston on the rod correctly( some are offset ) was the clip fully seated? Did you forget to install one of them altogether?

Funny fulltilt...I've only taken the head off at this point and inspected the cylinder and found the damage. (annoying "day job" keeping me busy) So before I just read your message I was upstairs making myself a coffee and had a eureka moment....I shouted ...ah ha!!...scared my wife. I thought...that wrist pin clip gave me such a hard time when I was putting it in. I bet I screwed it up some how and it fell out. The knocking was probably the wrist pin knocking around and the chunk taken from the cylinder wall was from the clip, or a piece of the clip or the clip took a piece of the ring. I figured since I didn't find anything in the cylinder from the top, It had to come from the bottom.

So I was sitting down to my computer to post about it hoping to impress you guys a little by blindly diagnosing it before disassembly since I was embarrassed by my failure.....But you beat me to it!!!

Anyway. Thank you for your post. I'm willing to bet you're right on the money. I'll post once the postmortem is done.

[Fulltilt]

"I thought...that wrist pin clip gave me such a hard time when I was putting it in. I bet I screwed it up some how and it fell out. The knocking was probably the wrist pin knocking around and the chunk taken from the cylinder wall was from the clip, or a piece of the clip or the clip took a piece of the ring. I figured since I didn't find anything in the cylinder from the top, It had to come from the bottom.

So I was sitting down to my computer to post about it hoping to impress you guys a little by blindly diagnosing it before disassembly since I was embarrassed by my failure.....But you beat me to it!!!

Anyway. Thank you for your post. I'm willing to bet you're right on the money. I'll post once the postmortem is done."




More than likely.
At any rate live and learn.
What I learned a long time ago was to never, ever re-use a pin clip. If you bugger it up installing it, for whatever reason...get/use a new one, period.
I never re-use the clips on hand helds, some do and get away with it, not me.

Though I have been known to form a plug of ATV to hold the pin in place...but only if I can't find where the darn clip flew off to...'cause I do professional work.

[lefty]

Good advice. They actually gave me two new ones with the piston, even though there was only room for one. There was a built in retainer on the other side. Well not really a retainer, more like it was machined that way. Unless I screwed that up too.

[Fulltilt]

Good advice. They actually gave me two new ones with the piston, even though there was only room for one. There was a built in retainer on the other side. Well not really a retainer, more like it was machined that way. Unless I screwed that up too.

You'll know when you open it up...

[Fulltilt]

Anyway. Thank you for your post. I'm willing to bet you're right on the money. I'll post once the postmortem is done.

So, what did you find out ???

[lefty]

So, what did you find out ???

So I finally got a chance to break this thing down tonight and see where I went wrong. I was disappointed.

Here are the observations:

As I brace myself for the I told you so's, the crank now has some pretty bad scratching on the journal. Way worse than originally. Originally, there was no texture to it but now I can grab it with my nail. This must be why she locked up on me.

Piston, perpendicular to the pin at the valves side and also at 180 degrees, has vertical scratching. Also, across from the valves perpendicular to the pin, there is a good nick / chunk taken out of the cylinder wall.

I was disappointed, as funny as that may sound, to find the wrist pin clip intact and in place.

Piston rings look intact and in place.

So as far as the crank and rod are concerned, I can blame the lock up on trying to salvage a crank that should have been scrapped.

But I have no idea what caused the damage to the cylinder and piston.

Conclusion: I suck at this. I know I was taking a risk with keeping the crank. So I understand the lock up. But I can't for the life of me figure out why I had damage to the piston and cylinder.

One thing I should have done, which I didn't, was strain the oil from the draining and examine it. I did not do that. I welcome any hypotheses, particularly regarding the knocking I heard. Please spare me comments regarding cost and return on investment. As I've said in previous posts, this is an academic endeavor.

[KE4AVB]

Conclusion: I suck at this. I know I was taking a risk with keeping the crank. So I understand the lock up. But I can't for the life of me figure out why I had damage to the piston and cylinder.

We all have failures...It when you don't learn from them it sucks. Chalk it up as good learning experience as least it was wasn't customer's engine.

As why it failed I have not a clue as I tend to be hands person during the inspections.

Question though did the rod turn loose as it can be the cause break out of the cylinder wall or it could have been part of the original failure just overlooked?

[bgsengine]

Piston, perpendicular to the pin at the valves side and also at 180 degrees, has vertical scratching. Also, across from the valves perpendicular to the pin, there is a good nick / chunk taken out of the cylinder wall.

I was disappointed, as funny as that may sound, to find the wrist pin clip intact and in place.

Piston rings look intact and in place.
.

Good practice for failure analysis - The gouge in cylinder wall - what shape does it take exactly ? how wide is it, how deep? Inspect the top pf the cylinder for any sort of ridge or any sign that installing rings might have peeled a bit of the ridge off - Also, review your cleanliness and installation and assembly procedures - did you use ring compressor? did you ensure it was *clean*? did you use clean oil to lubricate rings? do you recall any odd feeling of resistance while installing piston? inspect all the pieces internal to the engine - does anything look like a piece recently broke or chipped off? (gear teeth, fresh damage to block or base castings, etc) ?

Could there perhaps have been anything that "escaped" notice in the valve train? (chips of metal, carbon, etc) - could any part of the spark plug have broken off? (or anything that might have gotten stock in the plug?) - an examination of the size and shape of the gouge in your cylinder wall and then a search for the source might lead to clues..