Busted exhaust valves

[senor ding dong]

Got my 24k mile service done three weeks ago then last weekend on a trip to North Carolina (deals gap/cherohala) the bike loses power. Pull off the highway and the bike cuts out and I'm not able to start it again. Took it back up to chicago bmw (read: incompetent *********s) they try a few things (haul sensor, new computer) but nothing gets it running. I went over after work today to check on the bike (10 days have now passed). Neither the haul sensor nor the computer were the problem so they finally decided it might be a good idea to do a compression check. Right cylinder is fine, left one is zero. They remove the heads and find large voids missing from both exhaust valves. One is about a 1/16" diameter hole on the edge of the valve and the other is a 1/8 - 1/4" square missing on the edge of the valve.

Has anyone experienced this kind of failure with their S? What would cause the valves to break like that? Is it possible that they did something during the 24k mile service that would lead to the valve breakage?

[ckcarr]

Never heard of it.

But a wild guess is when they, or a new mechanic did the valve adjustment they were not at TDC on the compression stroke for that cylinder. So there might have been some real metal to metal contact between valve and piston. Might have lead to an imminent failure.

But the more I read, the more I realize these engines are just like all the others out there. Sometimes odd things break.

[MoDog]

Just one more reason to do the work yourself.

[alq2]

Sounds like burnt valves. Least the heads didn't break off and hole a piston and bend a rod. Kind of a coincidence that it happened just after the service. You think they could have adjusted the valves too tight?

[markjenn]

Most likely scenarios:

+ valves adjusted too tight, overheated, failed
+ severe detonation (could be bad gas)
+ defects in valves since new

Stuff happens and you should be able to get new valves under warranty or at reasonable cost. I'd fix and motor on.

- Mark

[Bails]

After service? No valve clearance,hence Valves not seating,hence burn near outer edge of valve.

[on2wheels52]

It would be good to know what the clearance settings were on the left side. Does the shop have a reasonable explaination for what occured?

Jim

[levert]

Too tight valves....
Yuck.
I was lucky ,or maybe unlucky, I had the valves done on an old honda 400 at a local shop. I was lucky they did them so tight the bike ran for 30 seconds and once heated just sputered to a stop.Mine was okay because the motor wasn't warm enough to melt the valves as yours did.Oh and the chain was adjusted so my wheel could barely turn.
I would have been better off having Ricky from trailer park Boys doing the service.
? now is will they accept responsibility?

[ckcarr]

" now is will they accept responsibility?"

No, nor can it be proven I don't think. Wonder what the repair cost estimate is?

[roger albert]

Tough to prove, but if it truly happened immediately after a service, they might be willing to work with you. Public name-calling is not likely to help that, I'd think.

Not enough info is really provided to diagnose anything here.
Which edge of valve? Where is valve damage w.r.t. other valve?
What about piston top? What about remainder of valve face? What about valve seat?

Too tight, or adjusted at other than TDC or coincidence are the main options. No high-rpm downshifts?

[bradzdotcom]

i'm with roger.
a picture would be great, but i guess not probable.
there's a lot of forensic science that goes into exploded parts.
in racing, the remnants are scrutinized, photographed, x-rayed, etc. Then they're bagged, tagged and shipped off to the mama-san country for further poking and proding.
every factory race bike gets a complete autopsy after each event, regardless of whether it finished first or 20th.

in addition to roger's questions, i'd be asking:
are there little balls of metal melted in there?
see any ragged edges?
can you account for all the pieces?
is the perimeter of the failure area the same color as the rest of it?

can you take these and roger's questions, plus a few others, and ask the guys who are doing the work?
it probably won't affect the outcome, but as you can tell, we all love a mystery and thrive on hypothesizing, pontificating and, most importantly...being right.

ps: my guess is incorrect valve adjustment too. it wasn't 180 degrees off, but i'll bet somebody was in the process of turning that motor and was interrupted by phone, roach coach, look at pretty girl in parking lot, etc....came back and didn't roll your baby over the rest of the way. got hot, went boom. (just a guess).

[flynbmw]

It happen to one of my exhaust valves on my '99 at 44,000 miles. I was able to nurse the bike home with a passenger and full bags (about 50 miles). Tough motor!!! The valve is sitting on my computer... My extended warranty covered it... Never found out why...

Ricky from "Trailer Park Boys" did not work on it... (funny show!!!)

Harold

[levert]

Sad but true is that Ricky is probably better than alot of mechanics.
For those of you who have not seen Trailer Park Boys catch a show!My wife grew up in that area and she says its pretty close to the real thing.

[Rapid Dog]

Not very common for sure, though, I heard recently that oil head RT's have a burned valve syndrome, usually due to leaness...
I couldn't believe after a carb rebuild and decarbonizing my airhead dropped a valve seat right in my garage while idleing...due to being too lean on that side.
Any thoughts pontifications,or hypothesis' here?....

[Dale Flowers]

You don’t say how many miles out of Chicago you where when the bike quit. If it were due to valves set at other than TDC it would have started acting up early on in the trip assuming it caused a metal-to-metal interference. And there should be signs of the violent event. If the valves were set too tight it would most likely take a while to burn them while cruising on the slab with low loads on the engine. As mentioned earlier I would want to know what the remaining valve gaps are to see if an error exists throughout.

[roger albert]

Agree with Dale

Rapid, that can definitely happen to airheads that idle too long, even with proper mix. Much more quickly with improper mix.
But, more likely is a head problem. To get an airhead motor to run that much more leanly to cause that kind of extra heat at idle is tough, as it usually won't idle that low period. That of course assumes some goof didn't have the other cylinder pulling hard enough to make up for the extra lean one on the other side.

Far more likely is that the head was just hosed, or it was let idle too long (or a combo) Idling too long, especially a fast idle, will drop a seat pretty easily.

[Rapid Dog]

It was a brisk test run with some on-road carb adjustment.
I came back and tried to synch again, let it cool then started it up, it idled a few revs and and "clank" it went, just like that.
Weird. That was my learning curve I guess.

[roger albert]

Probably overheated during the post ride second sync.
Ultra easy if you don't have a fan. Even then, it usually implies
the seat was loose in the head to begin with, so you shouldn't feel too badly. Part learning curve, part defective head discover.
Just had to do the better part of $700 of head work on a /2 for that. Much more susceptible than later airheads or oilheads. Especially when someone has buggered up a sparkplug repair.

[senor ding dong]

Thanks for the resonses and info guys.

Sorry no pics, I didn't have my camera with me and I don't remember the orientation of the voids. The piston head didn't have any obvious indication of metal on metal contact with the valves.

"Does the shop have a reasonable explaination for what occured?" The service manager offered no explanation as to how this may have happened. He claims that he'd never seen anything like this before. They've never been too inclined to take responsibility for anything in the past and I don't expect them to start now.

A little more info for your hypothesizing and pontificating: I was about 80 miles into the trip when it broke down. All interstate to that point, I was cruising about 70 - 75 mph and slowly rolled on the throttle to pass a truck. That's when the bike began to sputter. No high rpm downshifts. The tach needle was dancing around 4000 - 4500 rpm without going anywhere. That's when I pulled over and it stalled before I came to a full stop.

Knowing that there were large pieces of fragmented metal in the cylinder, concerns me about what it did to the cylinder walls, rings, etc. Not to mention what condition the right cylinder valves are in. After all this, my confidence in the Chicago BMW service department is seriously shaken. I appologize for the public name calling, but I'm sure you can understand my frustration. Paying $500 for a service in which they very likely set the valves incorrectly which resulted in damage to the bike and ruining my trip. I don't mind missing work but don't ever mess with my vacation!

[Anton]

How much carbon buildup was there in the head?