Honda 2003 225 hp broken valve catastrophic failure

"My 2003 225 with 170 hours had the #6 cylinder problem (water entering through exhaust). I was very indebted to members of this board - especially W D Neal - for their helpfujl advice. It has been in the Honda shop the past three months (over the NZ summer) whilst we negotiated repairs. They did a full service, and handed it back to me last week. Five hourson, at about 4000rpm and in good conditions it went BANG. Literally, BANG. And stopped.
Back to the shop: inlet valve on #3 cylinder disintegrated (see pix). This is the opposite side to the one that had been worked on. This head had not been removed. Problem is to find cause. Shop did decompression and leakdown tests before releasing it to me: all good. Therefore (they say) not a bent valve. One theory is the valve seal came free.
I would appreciate any thoughts, speculations or deep knowledge. I have some other pix & can answer questions. Big question in my mind is why this happened just 5 hours after a major overhaul. Seems to me the two events should somehow be related. Thanks for your input.
Stbd Cylinder Head"">Stbd Cyl Head 2

"Well I'm certainly no exp

"Well I'm certainly no expert at all, but it does concern me as I have a Honda 150.

From what I've read the valves are inertia welded to the stems and the weld can fail. Is this maybe what happened here? Supposedly it normally happens after lots of hours of high RPM running.

I hope someone experianced in these matters will post his opinion of what may have happened here"

"Wow! What a picture! Brutal.

"Wow! What a picture! Brutal.

I'm no expert either but, from the picture, it sure does look like the head of that intake valve just popped off and jumped right under that exhaust valve.

From the looks of the combustion chamber, she did several turns before she stopped. If it were mine, I'd take that head to the best big city machine shop I could find and ask/pay them to do a failure analysis on the components.

Inertia or "friction" welding of engine valves is a highly precise method that has been used for attaching engine valve heads to valve stems for decades.

The reason that it is used for this, is that it attaches two dissimilar metals~like the tough and hard valve stem to the heat tolerant valve head~while retaining 100% parent metal strength at the interface. So, I wouldn't fault the process but it certainly is possible that the application got screwed up at assembly.

If you take all the components(head, piston, valve stem, retainer and spring) to a good ENGINE machinist, he may be able to help you identify what failed. It should be fairly easy for a trained eye with a comparator or magnification scope to determine why that valve separated from the stem."

"Thank you for these thoughts.

"Thank you for these thoughts. I will take it to a head shop on Monday. Meantime, do you hold any thoughts about the timeline: ie the probability that this event is related - somehow - to the recent full service asnd exhaust modification, even though the work was done on the other bank.

It has been suggested that wshen the other bank was being worked on and the air filter was off some foreign material inadvertently dropped in and ultimately found its way to the #3 cylinder. Your thoughts on that would be welcome.

To me the timing seems important and I cannot easily believe that the two events are not somehow linked.

Again, ideas and speculations, as wild as you care, are most appreciated."

"Well, yes, anything I could a

"Well, yes, anything I could add would, indeed, be just that, wild speculation. So, that sounds like fun...I'll do it!

I don't know these big Hondas at all so I have no insight to offer as to the exhaust/water intrusion issue I've read about here. From looking at your photo, I can't tell if water were entering that cylinder.

If there was a mistake made at your shop I would say that it would probably been along the order of not crossing "T"s and dotting "i"s. To explain:

I'm not sure what you mean by "we negotiated repairs" and "they did a full service". If you (and they) mean a FULL service such as tune and lube, that MIGHT lead me to believe that they did a valve lash check/adjustment. If that is the case and the machine shop determines that the valve head was forced off of the valve stem through contact with the piston, then it's quite possible that something got in there or that the tech made a mistake or just didn't perform an adjustment on a too tight valve. However, with only 170 hours on that motor I doubt that the valve lash would be too tight from wear.

But, like I said before, it sure looks like the valve just popped off the stem and that would indicate a faulty weld just as Everett speculated earlier. In that case, I'm not sure what recourse you would have as the engine is clearly out of warranty on age. But, if there were a recall for that or a known history of valve to stem weld failures, you might be able to pursue that with Honda if you had purchased the engine new.

I will be very interested in what you may learn from the machinest."

"You can rule out water penetr

"You can rule out water penetration into any of those holes...no sign of it there. Engine timing could have been off, piston slapped valve and snapped off the valve. I would think this is one of a few hopes you have for there being a link to the work just done. Timing effects all cylinders. I would pull the other head again as well and look for signs of clearance issues. If another piston or valve shows nicks/damage it points in that direction."

"UPDATE: thank you all for a r

"UPDATE: thank you all for a remarkable and insightful range of possibilities. I am very grateful, and your comments have significantly helped my thinking (and that of local experts here in NZ). I have posted this on two boards, and the willingness of you all to so readilycontribute your expertise has taken me by surprise.

Today I took the head and valves to a specialist engineering shop.
The fellow (Wayne) had already told me he would also want his partner to look at the head. However, Wayne did say, quite quickly after close inspection, that he had a clear theory. He would not say until after his partner has also seen it. That will be next week when he returns from leave.

So this is an interim report from me. When I hear their views in about a week's time, I will report back.

Meanwhile, thanks a bunch.

Michael"