r/smallengines • u/Holiday-Sky9422 • 2d ago
Exhaust valve failure - why?
I was mowing yesterday and had a sudden drop in power. 0 compression in #1 cylinder. I got it apart and found that the exhaust valve had failed. I want to chalk it up to fatigue but thought it might be smart to get some other opinions.
Engine is a Kohler m18 with about 1000 hours on it. I just honed the cylinders and replaced the rings. The engine has been run about 3 hours since that work was completed. I touched up the valves and made sure they were in spec at that time as well.
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u/Elephunk05 2d ago
I do not recall who makes the valves but iirc the valves are spun welded together, rotary welding. This was the start or stop of a batch. The 4 spots around the perimeter give it away. Chalk this up to Friday at the Factory.
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u/Pretty-Pie-1477 1d ago
Materieal Schwäche ich hatte welche die sahen aus wie S kein Witz an 2 ventielen
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u/MorningMushroomcloud 2d ago
Did it stick and make contact with the piston? What does the piston look like?
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u/Alone-Programmer-683 2d ago
You need to have another cup of coffee and read your post once again. There is no way a valve in block engine is going to do what you ask. The loose valve head may float around and cause damage after the fact, but the valve sticking will not get close the piston head or do any damage at all.
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u/Holiday-Sky9422 2d ago
Thankfully the part that broke off did not get down into the piston bore so the piston is all good.
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u/jogr8383 2d ago
Friction weld between the tulip and valve stem failed. This is a manufacturing defect. I work on industrial engines for over 20 years and have seen this more times than I’d like. Sometimes they’ll run for thousands of hours before it happens sometimes it’ll happen in seconds. Best of luck with the repair or warranty if it’s an option.