Exhaust valve hit piston

[99yam40]

Too small for a drain, I'd bet that crap you found in the system caused no oil to the valve(stem/guide) and following failure-valve not closing / seizing up in the guide, then getting nailed..

Did you drain the oil yet and see if any clumps/crap comes out? Much if any sludge on the head (where the oil would be)?



*Now, IDK the answer but to prevent later failure, should that gunk be in the pan/oil system, how to clean the oil system W/O a full, engine break down??
Many oil changes, oil additives, ?

I have to wonder where this hole is located, and why oil came running out after he wiped across it removing some debris.
I have a feeling the motor was not running when he did that, and he would not have a pressure pressure port open in the head while the motor was running

[B3njammin89]

I have to wonder where this hole is located, and why oil came running out after he wiped across it removing some debris.
I have a feeling the motor was not running when he did that, and he would not have a pressure pressure port open in the head while the motor was running

The small hole was located right on top of cylinder head next to where the camshafts mount. Yes, the motor was not running when I did it.

[B3njammin89]

Too small for a drain, I'd bet that crap you found in the system caused no oil to the valve(stem/guide) and following failure-valve not closing / seizing up in the guide, then getting nailed..

Did you drain the oil yet and see if any clumps/crap comes out? Much if any sludge on the head (where the oil would be)?



*Now, IDK the answer but to prevent later failure, should that gunk be in the pan/oil system, how to clean the oil system W/O a full, engine break down??
Many oil changes, oil additives, ?





.

TownsendsFJR1300 yes I drained the oil but have not had time to filter through it to see if I can find any debris in it. The previous owner told me he did oil change but I doubt it. My motor only takes about 3.9 qts I believe and it had almost 5 in it. I’m thinking it may have been contaminated with fuel from the old low pressure pump possibly leaking fuel into the oil. I will take old pump apart to see if I can find a pin hole in the diaphragm. I’ve heard of those diaphragms going bad causing oil level to go up. It was well above the hatch marks in the dip stick.

[B3njammin89]

TownsendsFJR130099yam40 the machine shop got back to me and said they found about an inch of a piston ring lodged up in the exhaust valve. Ever heard of that happening on these Yamaha 115s? I just looked at the number 4 piston cylinder wall and the bottom part of cylinder doesn’t look scored but it’s not smooth. Looks slightly black with a texture to it. Is this something I can get re honed and replace the piston?

[TownsendsFJR1300]

And your NOT missing the top of the piston around the edge???.

Broken rings / pistons can happen to any engine, but for a piston ring to "lodge into a valve", it has to pass the top of the piston.

Anyway, I've read here the piston can be replaced but of course your going to have to tear down and see how damaged the block is.
I believe you can go up .010" on one piston / cylinder however someone else needs to chime in or do a search on this site.

Member "Rodbolt" would have posted about it (Master tech)..


Not to second guess the machinist, but could he have mistaken a valve seat dislodged? Something doesn't add up...….

[B3njammin89]

And your NOT missing the top of the piston around the edge???.

Broken rings / pistons can happen to any engine, but for a piston ring to "lodge into a valve", it has to pass the top of the piston.

Anyway, I've read here the piston can be replaced but of course your going to have to tear down and see how damaged the block is.
I believe you can go up .010" on one piston / cylinder however someone else needs to chime in or do a search on this site.

Member "Rodbolt" would have posted about it (Master tech)..


Not to second guess the machinist, but could he have mistaken a valve seat dislodged? Something doesn't add up...….

You’re thinking how I’m thinking. I can’t imagine how the piston ring piece fell out without breaking the piston. After I told him that all the pistons are not broken he thinks may be previous owner put in new piston rings and maybe left a old piece of piston ring in there when putting everything back together. I asked him if all the valve seats looked good and he said yes. My only other guess is that piston ring did not come from my cylinder head but he claims that it did. I saw the table he was working on and it did not look very clean.

[B3njammin89]

he gave me the broken piece and it is almost an inch long and perfectly flat. I would think that piece of “piston ring” would at least be bent as well.

[zenoahphobic]

You’re thinking how I’m thinking. I can’t imagine how the piston ring piece fell out without breaking the piston. After I told him that all the pistons are not broken he thinks may be previous owner put in new piston rings and maybe left a old piece of piston ring in there when putting everything back together. I asked him if all the valve seats looked good and he said yes. My only other guess is that piston ring did not come from my cylinder head but he claims that it did. I saw the table he was working on and it did not look very clean.

Some people simply don't understand about being clean and tidy. This places doubt about the origins of that "piece" and the value of the mechanics diagnosis.

[TownsendsFJR1300]

Some people simply don't understand about being clean and tidy. This places doubt about the origins of that "piece" and the value of the mechanics diagnosis.

Yup, piston rings can't re-appear on the other side of the piston on a 4 stroke without damage to the piston-just ain't happening..


Can you post some good pic's of the cylinder here?

Can you catch a fingernail on the cylinder wall that's in question?


Depending on how bad that scratch is, is what you'll need to do next..

Best case, put the head back on and do a leak down test.
Worst case, tear down, fix the cylinder and replace the piston..

[B3njammin89]

Yup, piston rings can't re-appear on the other side of the piston on a 4 stroke without damage to the piston-just ain't happening..


Can you post some good pic's of the cylinder here?

Can you catch a fingernail on the cylinder wall that's in question?


Depending on how bad that scratch is, is what you'll need to do next..

Best case, put the head back on and do a leak down test.
Worst case, tear down, fix the cylinder and replace the piston..

TownsendsFJR1300 I will try and convert the pics on my computer to pdf so it will allow me to upload in the morning. The walls aren’t scratched but it has this black build up that I tried to buff out with oil and a piece of emery cloth. Some of the black stuff In the cylinder wall came off but I didn’t want to keep sanding down on it too much. After getting some of it off it still feels hard almost like it’s embedded in the cylinder. Not sure if carbon build up gets hard to the touch like that or not.

and the black crud stuff in my number 4 cylinder wall feels more of a bump rather than a dent.

[B3njammin89]

Cylinder wall #4

[B3njammin89]

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[ausnoelm]

I would be very surprised if that piston has part of a ring missing, also there would be marks on top of the piston where it bounced around for a while if something was in the combustion chamber, I think your "mechanic" is just telling you rubbish.

[B3njammin89]

[zenoahphobic]

Looks like something like water has sat in the bore for awhile, the rust somewhat ground away when the engine eventually was turned.


I would carefully wipe that spot with petrol and then acetone to remove all oil. Then apply a rust dissolver (phosphoric acid). If it indeed was corrosion the metal should become clear or shinny. Remember to then reoil before turning the engine over again. Not good to use sandpaper, proper honing needs to be done if there is enough space above the piston.