OH, Goody - a broken valve

[longdog]

Thanks, that's oddly reassuring. Like being told in the middle of a tornado that your tie is still straight. although, in my case, that would be a worry as I haven't worn a tie for five years.

So, summing up, the perceived wisdom is:-

DON'T leave it on the side stand
DON'T start the engine
DON'T change gear
DON'T Rev it up
DO use axle grease instead of engine oil.

Is there anything I've missed?
Is it alright to just look at it dreamily while polishing it?

DON'T use it?

 

[Steptoe]

It would be helpful to know which valves tend to drop - exhaust or inlet, top or bottom.

Exhaust. Could be top or bottom.
I've had a few 1150 but no 1100 models with dropped valves.

BMW used to have the valve head welded to the stem at the exact point where the stem protrudes into the exhaust gases and the end of the guide. Hence a service life of 50k miles.

You used to be able to get a swiss made valve with the weld further up the stem so it was out of the way of the exhaust gases.

 

[Deleted account 111026]

R1100GS, 142K km, centre stand removed 6 1/2 years ago, can be left on side stand for up to 4 weeks between runs, absolutely no problems.

 

[millard]

Exhaust. Could be top or bottom.
I've had a few 1150 but no 1100 models with dropped valves.

BMW used to have the valve head welded to the stem at the exact point where the stem protrudes into the exhaust gases and the end of the guide. Hence a service life of 50k miles.

You used to be able to get a swiss made valve with the weld further up the stem so it was out of the way of the exhaust gases.

Steptoe
As you've probably seen and experienced more of this than most of us here, do you have any theories about why it happens? and how to avoid it?
Or do you think that the weld position mentioned in your last post the cause of it?
millard

 

[Gipsy]

If parking on the side stand IS going to be the cause, then what about all those 1200Ses which don't come with a centre stand in any case???

I was going to ask the very same question.

 

[Timolgra]

Side stand is a red herring imo, you could put the same argument forward regarding the upper shell of a big end bearing etc. etc. etc.

 

[Sgt Bilco]

Can`t believe it`s a side stand thing. What abour radial engines

 

[Mav]

My HP2 doesn't have a centre stand and it's managed 21,000 miles

 

[Steptoe]

Steptoe
As you've probably seen and experienced more of this than most of us here, do you have any theories about why it happens? and how to avoid it?

Don't change the engine oil before a new moon.

Or do you think that the weld position mentioned in your last post the cause of it?
millard

I was talking about airhead engines. The break used to happen at the join betwen head and stem

 

[millard]

so we're as wise as ever then eh?

 

[turnipbmw]

I was told the airhead valves were 'friction' welded by spinning the head against the stem.

But the reason they break is down to valve guide wear causing the valve to be opened at more and more of an angle.

When I fixed them for the Police, the exhausts did occasionally break at about 40,000 miles (especially if the plod owned a ZZR1100 and hated the R80)


If you ask me though, this problem has been blown out of all proportion.

'Trial by forum'

Cant imagine anyone even bothering to mention a dropped valve at 23,000 miles on the ducatisti website

 

[cookie]

i've heard that the reason for airhead valve failure was due to guide wear as well, but that it was the valve not hitting the seat square that was the problem.

 

[Tricky]

This is shocking.

PLEASE rmalc.whatever@interwebblahblah can you change your forum name to something shorter.

Many thanks




Oh and hope your bike gets fixed ok. Its a mechanical thing, it might go wrong from time to time

 

[MattW]

As I said previously, I think the parking on the side stand issue doesn't ring true. My best guess would be a cooling issue - could well be idling on the side stand but given the well known warnings, do any oilhead riders (except the police) ever do that? From what I've heard 1200's run lean anyway, so cooling might be a bit marginal and other factors could tip marginal cooling in the right hand exhaust port area over the edge.

Low oil level?
Crap servicing?
Non standard pipes?
F*cked about with in other ways (chipped etc)?
Thrashed (might not even require thrashing), turned off immediately and parked on the side stand so that the uphill cylinder drains quickly causing 'heat soak' to overheat the exhaust valves? (My favourite theory....)

 

[John Armstrong]

Coriolis effect

Exhaust gasses exit the LH pot the right way and the wrong way on the RH pot = RH pot fails. QED

All related to Buys Ballot's Law: http://en.wikipedia.org/wiki/Buys-Ballot's_law

 

[[email protected]]

I was told the airhead valves were 'friction' welded by spinning the head against the stem.

But the reason they break is down to valve guide wear causing the valve to be opened at more and more of an angle.

When I fixed them for the Police, the exhausts did occasionally break at about 40,000 miles (especially if the plod owned a ZZR1100 and hated the R80)


If you ask me though, this problem has been blown out of all proportion.

'Trial by forum'

Cant imagine anyone even bothering to mention a dropped valve at 23,000 miles on the ducatisti website

If it were a Duke, then you'd expect it to make the website if it hadn't destroyed itself or gone into a terminal Italian sulk by 23,000 miles. But, from the Bavarian ironfounders' association, I expect a minimum of 100,000 miles. As I said, I have a 730 at 202,000 miles, and I expect to get another 200k. out of it.
If it had gone at 40,000 - well, I might just say I was unlucky. 23,000? for a Beamer this is brand spanking new.

 

[Timolgra]

F*cked about with in other ways (chipped etc)?

It would probably run richer if it were chipped.

 

[MattW]

It would probably run richer if it were chipped.

You may be right - just speculating, but his one's my favourite:

Thrashed (might not even require thrashing), turned off immediately and parked on the side stand so that the uphill cylinder drains quickly causing 'heat soak' to overheat the exhaust valves? (My favourite theory....)

There's a lot of residual heat in the head and exhausts and when you turn the engine off, you also switch off the cooling of the high flow oil circuit (which is targeted at the exhaust ports). I could imagine this leading to overheating of the the valves.

If someone was sufficiently motivated, it would be quite easy to investigate too (datalogger and a couple of contact thermocouples).

 

[Steptoe]

There's a lot of residual heat in the head and exhausts and when you turn the engine off, you lose the cooling of the high flow oil circuit (which is targeted at the exhaust ports). I could imagine this leading to overheating of the the valves.

.

The cooling depends on the valve being closed. The head absorbs the heat. So it all depends on luck which valves come to rest closed when you turn the engine off.

The 1150 models i've had in which have dropped a valve have been on both left and right sides so the side stand parking seems irrelevant with those models. But funnily the RT models outnumber any other model. And the mileages have all been fairly low, from 16K .

And it's more common than people think. Maybe because people seem to want to sell the bikes on as soon as they've been repaired so have no incentive to shout it out loud, so it's kept quiet.

 

[John Armstrong]

The 1150 models i've had in which have dropped a valve have been on both left and right sides so the side stand parking seems irrelevant with those models. But funnily the RT models outnumber any other model. And the mileages have all been fairly low, from 16K .

So, the RT engine isn't as open to the airflow as the GS is, that might be helping the heat not to be removed by airflow? I guess the Police bikes in London etc spend a high proportion of their time at slow speeds in towns. Unlike the usual GS rider