Exhaust valve hit piston

[TownsendsFJR1300]

The piston doesn't look bad at all, I'd leave it..

The cylinder looks really good too...



If you look at the black stuff, it appears the engine was partially tilted, the piston halfways down in the stroke and a "liquid" gathered right there. The top piston ring stopped further "flow".
The "track" looks like the substance ran towards the head (once it was full).

And yes, carbon can be very, very hard. I suspect that's what it is. The engine sat for awhile somewhat tilted.



I'd take lacquer thinner, carb cleaner, maybe soak a small cloth and let it sit over the substance to dissolve. Then use a tooth brush, and scrub it off.

KEEP THE ENGINE TILTED SO THE THINNER RUNS OUT AWAY FROM THE PISTON...



I personally wouldn't tear down any further. Work on that substance, make sure your oiling system is clear.



Attach the head and do a leak down test.
The leak down test is done at TDC, compression stroke normally. **I'd do the test again with the piston rings in that area (both valves closed) and check results- I suspect you'll be well within spec's.







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[TownsendsFJR1300]

The site just eraser 15 minutes of typing...………


The piston looks to be in good shape as does the cylinder short of the "black stuff".

+100 re Zeno's analysis. A liquid accumulated there, sat for quite awhile, excess flowed towards the head.


That stuff was there way before the valve hung up open and very likely didn't have anything to do with your failure.


I wouldn't tear down further and proceed as Zeno noted.

Again, make sure the oil passages are clear..





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[B3njammin89]

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.

zenoahphobic I will try that. Can you recommend any good rust dissolvers for a cylinder wall or should I simply just pick one from the auto store or not store?

[B3njammin89]

The site just eraser 15 minutes of typing...………


The piston looks to be in good shape as does the cylinder short of the "black stuff".

+100 re Zeno's analysis. A liquid accumulated there, sat for quite awhile, excess flowed towards the head.


That stuff was there way before the valve hung up open and very likely didn't have anything to do with your failure.


I wouldn't tear down further and proceed as Zeno noted.

Again, make sure the oil passages are clear..





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Ahh man, I’m sure it was some good knowledge coming my way too! I will wipe the wall oil free and apply the rust dissolver as you both recommended. I appreciate all the feedback from you and everyone.

TownsendsFJR1300 I would hate to think the machine shop was trying to get over on me thinking if he told me he found a piece of “piston ring” in my cylinder head to persuade me to bring my cylinder block as well for work that is not needed.

[TownsendsFJR1300]

That discoloration was there way BEFORE you had the valve issue...

The engine NOW, with the valve replaced, (and hopefully oiling system good) will run as good as before, perhaps better..



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[B3njammin89]

That discoloration was there way BEFORE you had the valve issue...

The engine NOW, with the valve replaced, (and hopefully oiling system good) will run as good as before, perhaps better..



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TownsendsFJR1300 Yes indeed, I’m hoping to be able to remove most of the black buildup and reinstall the head. Yamaha dealer told me I should receive the new valve next Tuesday

[B3njammin89]

TownsendsFJR1300 I found out the pistons in my motor are forged wiseco pistons after searching the numbers stamped on top. But when I search them they come up as 2001-2006 Yamaha 115 pistons. One site says pistons from 2001 to 2014 all fit the same block while other sites say 2001-2006 have a certain piston compared to 2006+ later models.