Interesting stuff.
OH, Goody - a broken valve
- Thread starter [email protected]
- Start date
Interesting stuff.
Bones
Registered user
They don't make 'em like they used to..........
.. but then they only used to rev to 4K. Perhaps they do make them like they used to but they should have redesigned
Any residual heat is small potatoes compared to the valve being held in a high temperature exhaust flame
( petrol actually catches fire when it burns ! )
as soo nas the engine is turned off the parts start cooling.
stop imagining stuff
Get away, I never new that
I bow to your obviously superior knowledge of thermodynamics and engine design - enlighten me - what makes the heads fall off 1200 valves then?
[email protected]
Guest
is it this?
Wonder whether it is something to do with "trip spectrum". ~Do people tend to use the side stand more if they are doing short trips - stop start running round shops etc.
i.e. do those who use the side stand most frequently have a different journey pattern? Frequent stops, don't always want to do the big heave, or not enough room in parking spaces.
Wonder whether it is something to do with "trip spectrum". ~Do people tend to use the side stand more if they are doing short trips - stop start running round shops etc.
i.e. do those who use the side stand most frequently have a different journey pattern? Frequent stops, don't always want to do the big heave, or not enough room in parking spaces.
Nice thought, but it's just as likely to be the coreollis effect during equinoctial gales
.The notion that oil runs off the valve stem because of the way it's parked is nonsense, just think about the valve set up on more conventional engines.
I'm not speaking off the top of my head, I was an engine fitter with Rolls Royce in a past life If it's any consolation, we had lumps of camshaft in the sumps, conrods through cases, valves embedded in pistons you name it, it's happened.
Metallurgy can be a black art
[email protected]
Guest
that means the boomerang throwers should have LH valve problems. But, then again, its no good asking them, they don't know left from rightNice thought, but it's just as likely to be the coreollis effect during equinoctial gales
The notion that oil runs off the valve stem because of the way it's parked is nonsense, just think about the valve set up on more conventional engines.
I'm not speaking off the top of my head, I was an engine fitter with Rolls Royce in a past life If it's any consolation, we had lumps of camshaft in the sumps, conrods through cases, valves embedded in pistons you name it, it's happened.
Metallurgy can be a black art
I believe that they run comparitively rich as they are configured for a catalyst which needs a richer mixture. The reason why car fuel consumption figures increased with the introduction of cats.
Another political con, bowing to the pressure groups financed by the companies that mine the palladium etc. used in the catalysts.
That makes no sense to me, why invent a device to clean up emissions that needs to burn more fuel, causing a negative impact on the environment it is meant to protect? Surely the catalytic converter simply 'catalyses' unburnt hydrocarbons when they are present, and is not 'fuelled' by them?
Surely any modern engine is designed to run the lean side of stoichiometric in the interests of meeting Euro 3 emissions targets for Co2 and unburnt hydrocarbons??
I must admit, that's what I thought, however I didn't want to jump in and make a fool of myself (again
)In fact don't over rich mixtures kill cats by blinding the matrix?
I was in the motor industry a long time ago but my knowledge is certainly out of date now.
I believe that the catalyst has to have a certain amount of unburnt fuel through it to achieve it's operating temperature hence the need for a comparatively rich mixture. During the winter the catalysts don't (certainly didn't) even work for the first 5-8 miles or so depending on the ambient temperature so for most vehicles they are a complete con and waste of money as the majority of trips are less than that distance.
At the time of the discussions prior to the introduction of catalysts Ford wanted to go another direction with "lean burn" technology utilising a stratified charge. They used the same statement as you have above and were convinced too that it was nonsense to introduce "clean" technology that required an engine burn more fuel. They were up against some very interested parties with a lot of money, companies like Johnson Matthey (http://www.matthey.com/), who knew that catalysts would ramp up the need for semi precious metals enormously and in the process make huge fortunes.
Ford lost the argument and cats became the norm. Whilst they (cats) have now received a lot of development it certainly was as I stated when they were first introduced. Maybe things are better now but I wouldn't bank on it.
[email protected]
Guest
And now it's back
Just collected the bike from PREMIER BIKES of DIDCOT. 01235 519195
I want to comment on their terrific no-quibble attitude.
They collected the bike and did the repair without a murmur as it was within the three month warranty period. I know that is their obligation, but they still did a good job without any hesitation. The retail bill would have been £1070, including VAT and I know they got no joy out of BMW who just shrugged.
PREMIER are a KTM dealer, and they tell me they will not be handling any more BMWs for a while. If I were a KTM owner, would be very happy to have them look after my machine.
Interestingly, it doesn't seem to pop so much on overrun/neutral throttle, so I wonder if something was not right with it before.
Just collected the bike from PREMIER BIKES of DIDCOT. 01235 519195
I want to comment on their terrific no-quibble attitude.
They collected the bike and did the repair without a murmur as it was within the three month warranty period. I know that is their obligation, but they still did a good job without any hesitation. The retail bill would have been £1070, including VAT and I know they got no joy out of BMW who just shrugged.
PREMIER are a KTM dealer, and they tell me they will not be handling any more BMWs for a while. If I were a KTM owner, would be very happy to have them look after my machine.
Interestingly, it doesn't seem to pop so much on overrun/neutral throttle, so I wonder if something was not right with it before.
that could very easily have been a lot worse.
What about the R1100S and 1200S which don't have sidestands fitted.
If it was because bikes are left on the sidestand the "S" models would be the first to drop valves, and i've never had one in.
That could be taken as BMW are far too reliable and they can't make a living as the bikes are never in the workshop.
But KTM's on the otherhand are good earners
[email protected]
Guest
I'm not pushing KTM, although rubbish they ain't - look at their competition record. I wanted to comment on Premier's attitude. I've had more dicking around from main dealers, with questions about what I had been up to with their whatever it is. These people just got on with it.
People of Didcot, you've got a good bunch there.
People of Didcot, you've got a good bunch there.
Back to the original subject, how does an engine 'drop' a valve? It can't be the pistons fault as it just reciprocates, therefore it must be valve train related. My guesses are:
1) Valve bounce during excessive RPM causing piston to valve contact.
2) Incorrect valve timing causing piston to valve contact.
3) Excess guide wear causing valve head/seat wear leading to failure.
4) Metal fatigue of repeatedly stressed area of valve stem.
5) Poor materials (inclusions/dislocations at the grain boundary) leading to component failure.
6) Combustion temperature exceeding design limits due to incorrect fuelling.
7) Failure of valve head at the weld junction (heat affected zone).
I was also wondering if it were possible for the camchain tensioner to lose tension during engine running (partial drop in oil pressure ?), altering the valve timing enough to allow piston/valve contact. Unlikely I know.
Anyone care to guess which of the above it could be, or shed any more light on it?
1) Valve bounce during excessive RPM causing piston to valve contact.
2) Incorrect valve timing causing piston to valve contact.
3) Excess guide wear causing valve head/seat wear leading to failure.
4) Metal fatigue of repeatedly stressed area of valve stem.
5) Poor materials (inclusions/dislocations at the grain boundary) leading to component failure.
6) Combustion temperature exceeding design limits due to incorrect fuelling.
7) Failure of valve head at the weld junction (heat affected zone).
I was also wondering if it were possible for the camchain tensioner to lose tension during engine running (partial drop in oil pressure ?), altering the valve timing enough to allow piston/valve contact. Unlikely I know.
Anyone care to guess which of the above it could be, or shed any more light on it?
Out of the list 5, 6 & 7 get my vote, but I'd add something along the lines of:
"fundamental failings in the design of the engine resulting in normal running temperatures exceeding the capabilities of valve train"
Basically the boxer twin has gone as far as it can (or slightly too far) without some serious redesign of the cooling system and / or valve train. The current oil / air cooling system just can't cope with the specific output of the engine.
I can see watercooled heads in the future, just like Porsche did....
What about: http://www.telegraph.co.uk/motoring.../2749981/BMW-HP2-Sport-Question-of-sport.html or doesn't it count on the taking the boxer forward?
Of course it counts as taking the boxer forward, however that engine is pretty far removed from the 1200 in the GS. Perhaps if that engine was put in the GS they wouldn't be dropping valves, however the engine costs a bleedin' fortune to make and the GS would probably cost £15k+ and no-one would buy it (or they'd have to sell at break even).
Notice the bit where I said "without some serious redesign of the cooling system and / or valve train", which is exactly what they've done
Similar threads
