Valve gone AWOL

[Brendan]

Hi Folks, well it's just happened to me.
Top exhaust valve on right side has taken up new residence in the piston. I have read the various posts regarding possible reasons for failure and you can eliminate the engine running while on the side stand as a cause.
I was travelling at about 20mph low revs and bang. Stopped immediately and did not try to restart so here is the damage caused.
My question is; Can I reuse the head given the amount of impact damage?
My own opinion is that it's fine and would be usable having cleaned up the damage and fitting a new set of valves ground in as necessary. Piston is definitely shot and needs replacement.

 

[(RIP) Bin Ridin]

Hi,
What mileage is on the bike?
Bin

 

[Pukmeister]

Wow, bad news indeed, glad you were going slowly.

If the head casting is OK I would be tempted to get the seats lightly recut and use it again with a new piston and rings after glaze busting the cylinder bore.

Did you have any warning symptoms?

What year is your bike ?

Is your bike modified from standard in ANY way eg end can, headers, K&N etc etc

 

[MikeP]

Are you certain that the international gang of 1200GS thieves hasn't stolen it?

I mean, first a kill switch, then wheel nuts, now this missing valve?

 

[Pukmeister]

Forgot to add, the conrod could be bent, maybe worth asking your BM dealer if they would pull the engine and change the rod, or just fit a new piston.

 

[Brendan]

No symptoms prior to the failure.
Year 2005
Mileage 20k miles
No engine or exhaust modifications.
No abuse
No offroad use
Used as an instructors bike following pupils mostly in Urban areas 30-50 mph area.
Occasional touring and outings, nothing too extreme.

 

[Noddy]

Do you have a picture of the remains of the valve top?

Just curious as the remains of the stem show that its hollow.

 

[Pukmeister]

Probably sodium filled for cooling like most exhaust valves.

 

[(RIP) Bin Ridin]

Manufacturing defect?
Ask BMW for their explanation?

 

[st247]

Manufacturing defect?
Ask BMW for their explanation?

'They all do that sir'

 

[Brendan]

Do you have a picture of the remains of the valve top?

Just curious as the remains of the stem show that its hollow.

Still stuck in the piston.

 

[T900]

the indentation at the valve seat is your main problem as the seat could come loose and screw it all up again. even if the seat is recut, it could still drop out of its seating in the cylinder head. particulary with an aircooled engine. if in doubt, get an engineering shop to check it out.
in my experience with car engines, exhaust valve failures always have an underlying cause eg air leaks causing the valve to run to hot, sticking in the guides due to poor oil quality or carbon build up. resulting in contact with the piston causing the valve stem to flex. valve clearance being to small resulting in the valve being held slightly open at running temperature. over reving due to changing down gear to fast.
the valve usually does not fail straight away. you may have noticed a lumpy idle prior to the failure,
yes i have over 25 years experience with engines

 

[Brendan]

or carbon build up. resulting in contact with the piston causing the valve stem to flex. valve clearance being to small resulting in the valve being held slightly open at running temperature. over reving due to changing down gear to fast.
the valve usually does not fail straight away. you may have noticed a lumpy idle prior to the failure,
yes i have over 25 years experience with engines

I noticed that the front ring (one nearest the top of the piston) is stuck in it's groove (no movement in the ring). The other 2 rings flex in and out of their grooves fine.

 

[Brendan]

Where would you think the air could have been drawn in?


No noticeable difference in idle, running or performance.

 

[MartinL]

Could it have been apart before? Those scratch marks on the gasket face look like a ham fisted attempt to clean it up with coarse emery or something.

 

[MartinL]

Looks very sooty / over rich too. I'd expect the carbon deposits to be a bit more tan / biscuity colour on a healthy motor....

 

[Brendan]

Could it have been apart before? Those scratch marks on the gasket face look like a ham fisted attempt to clean it up with coarse emery or something.

Bought the bike with 6k miles and no previous history. The scratch marks are inside the area where the gasket seats.

 

[Myke Rocks]

dropped valve

Cylinder head is fully repairable to "As New" standards, with no trace of the impacts remaining.
I watched an aquaintance who does such repairs doing Subaru cylinder heads a couple of weeks ago. Similar damage. He says that in 35 years, he has only failed to repair 1 cylinder head, & that was a couple of months ago. Off a Chinese forklift. He stated the cast iron was made of Ryvita!
Cast Iron, Aluminium, no combustion chamber or valve seats left, he does not care. Just fixes it. He always takes out the minor marks becuse he says that they provoke detonation.
(If you need one repaired, he does ships cylinder heads as well!)
If you cannot find anyone locally to do a perfect repair, I will provide contact details.
Myke
[email protected]

 

[RickG]

The picture of the the broken end of the valve is a bit interesting . Looks like a fracture but the different colours on the fracture face suggest varying exposure to the exhaust gasses and hence the suggestion that it's a crack that has developed over a period of time before finally letting go completely.

Assuming it's at least a two part valve, could it have cracked at the weld?

 

[Brendan]

Assuming it's at least a two part valve, could it have cracked at the weld?

Possibly, I haven't removed the valve from the piston or disassembled the head any further just yet.