Word of warning for twin cam owners

[Deleted account 200502001]

Ive recently dug up my driveway and relayed the concrete to form a sloped bank effect, that way when I put my side stand down the bike remains perfectly level. Its only fallen over seventeen times.

I suggested idling on the sidestand was the cause of RH cylinder failures ages back when I was a new member on here. I was laughed out of town, and made to scrub the yacht's decks for a week for suggesting it.

Shut up and get scrubbing

 

[MattW]

The problem is stupid owners walking away from the bike idling for long periods, not a sidestand issue. You would get the same on the centerstand. Until someone shows more than incidental speculation, it is a BS assertion!

Jim

Sure, It's just a hypothesis.
It's (generally) accepted that there is some sort of right hand cylinder head issue with 1200's and if we were being scientific about it, the onus is on those proposing the hypothesis to prove or at least advance the understanding of the issue as it relates to their hypothesis.

However back in the real world no-one is going to sacrifice a bunch of 1200's to try and work out what's happening (and BMW sure as hell aren't going to). So, we'll probably never find what the real problem is (assuming there is one).

So, we're going to get these assertions and rebuttals in forums like this and ADV for ever. The people with the theories will stick to them and those rebutting them will stick their fingers in their ears and call bullshit but without evidence it's all just speculation.

However, getting back to the theory in discussion here, it may be complete coincidence that the 'problem' occurs on the high cylinder when the bike is on its sidestand but I'm a big believer in Occam's Razor and without better evidence to say otherwise, I'm prepared to give credence to the theory that the two are related (I may be miss-remembering this, but I'm pretty sure the UK police instructed their bike cops to stop leaving their 1200's idling on their side stands - yes - it doesn't prove anything).

People rebutting the theory bang on about the fact that the lubrication system is high pressure pumped , oil film strength, etc, etc and they're quite right but I don't think the problem is a lubrication issue so none of that matters. My 'theory' is that it's more likely a cooling problem and that the 'high' head may be seeing a reduced cooling oil flow under certain conditions. As the cooling circuit is a separate low pressure, high(er) volume system and doesn't have oil pressure monitoring, we have no way of monitoring cooling flows so my theory is just as impossible to 'prove' as any other

But, I'll stick with starting and riding off (after a few seconds), trying not to idle it to long when hot (and certainly not on *any* stand), using decent semi-synth, heat tolerant oils and continuing with my private quest to work out a way of adding a cooling fan to the oil cooler (been trying to do this since if first got my 1100)

 

[littleredrooster]

However, getting back to the theory in discussion here...

...can I just point out that the original subject of the thread had nowt to do with valve failures; it was about big-end and main-bearing failure which is possibly a different jar of carp altogether...

 

[Blackal]

Just for info, the worst damage you can do to an engine is to rev it with no load. The components with in stretches far more than when it is under load placing more stress on the bearings and subsequently the thin layer of oil.

I would have said that the combustion pressure of full-load - would be what put the most stress on engine components, bearings included.

Al

 

[cookie]

...can I just point out that the original subject of the thread had nowt to do with valve failures; it was about big-end and main-bearing failure which is possibly a different jar of carp altogether...

yup. two entirely separate issues being confused here IMO.

 

[tanneman]

Not really, not so sure of it under acceleration but as you add load you also add friction that takes some energy away from the impact and stretch on the rods and bearings. The power stroke is dampened due to the inertia as opposed to the quicker reaction the crank would experience with no load on it. If there is no load it is a free spinning machine and the only place the energy can go is to deform the components apart from creating noise, heat etc. We are talking of 1000th of a millimetre so it can be calculated but not filmed. The oil film is more likely to stay in place under a gradual load application than a shock load. With finer tolerances and better materials and lubricants this can be limited but it is still steel in one form or another that is used so I wont go revving the tits of an engine. Mechanical sympathy comes to mind. Same as leaving an air cooled engine to idle on a hot day or getting a ball bearing to spin by blowing compressed air over it ouch.

If you mean by full load hard acceleration then I'll add that those people who spend more time at speed tend to age slower. Some clever guy figured that one out. The result will be more noticeable the longer you spend at or near the speed of light.

If going by Mattw and his explanation then there would not be a problem by having the bike idle on the centre stand, given that one cylinder is not higher than the other. Just to throw the cat amongst the pigeons but is there not a water pump made by Rosenhuaer (I stand corrected) for fire fighting duties that uses the 1200 hexhead engine in a portable frame. If so then the cooling function of the oil system is sufficient when on a level ground and being fire fighting equipment it would be a clean piece of kit so the design of the cooling fins is then adequate for this application. Having a low pressure feed going uphill is not as effective as a low pressure feed going downhill. But, as the OP points out the problem is with the main and big ends. This is in the sump so somewhere oil starvation has occurred. If the problem is not related to the oil pump, filter, pressure switch or non return valve then the oil had to go somewhere where it can't be circulated. A low oil level can contribute and if the circumstances are right then the little bit of oil that pools in the LH rocker cover is enough for the oil pump to cavitate and you loose oil pressure momentarily. Adding to this is an already hot engine and hot if not overheated oil and maybe the journals are scraping on the bearing surfaces every power stroke. The pressure switch may not be quick enough to react to the oil pump cavitation so the indication to the rider would be minimal.

To put it into perspective regarding the forces involved with-in the engine as some may view it a only a rotating mass. The Hexhead boxer is designed to develop 110bhp. An electric drill rated at 800W is more than enough to snap your wrist whilst drilling. The impact of the conrod journal powered by the combustion in a 500cc cylinder onto a bearing is a crushing load that can and will break through the oil film. You do need the constant flow supplied by the oil pump. The oil pressure is determined by the restriction the oil flows through (force over surface area) so the first place you are going to notice the loss of oil is where the surface are the biggest and that is at the main and big end bearings.

Yes cookie and littleredrooster.

 

[MattW]

...can I just point out that the original subject of the thread had nowt to do with valve failures; it was about big-end and main-bearing failure which is possibly a different jar of carp altogether...

True.
But the carp may be related if it's also a sidestand issue as mooted early on

Anyway, I've got my personal theories about the main bearing issue...

 

[Bendy toy]

I really can't see how the LHS cam cover on a BMW boxer can hold enough oil to drop the sump level enough to starve the oil pump. If it was that full would there not be oil smoke on starting from oil leaking past the valve stems.

600cc pistons and rods have a lot of internal inertia so take a lot of starting and stopping at any speed but at low idle speed they wont be moving smoothly. That clatter can't be good for the crank bearings oil film. How often do we notice a rattle at tickover thats gone when its run a few hundred RPM faster? Do that on a hot engine and expect trouble.

I've recently put an oil pressure gauge on my bike. From cold, at tickover, it shoots around 90psi then after a few seconds goes over 100psi. The pressure is clearly fine but Ive not seen any other engine do that. Why would pressure go up then go up again? Normal pattern is high pressure from cold that drops to a running pressure as the engine warms up. Ive not yet had it hot enough to see what happens with thin oil at tickover.
Edit - maybe its the pressure relief valve popping off as the oil starts to move.

Crank bearing failure could be riding style - hot engine, thin oil low revs, under load breaks the oil film. Slogging an engine is always stressful to the crank and rods. Mine with a power commander will easily pull a high gear at under 2000 revs, but I avoid doing it. Who knows what such slogging could be doing to the crank.

During WW2 Rolls Royce were developing the Crecy 24 litre sleeve valve 2-stroke based on the Merlin layout with the Merlin 2 stage blower. V twin bench tests estimated it would give double the power of a Merlin. But the full size V12 engines would regularly throw a conrod long before they were at full power. The V-twins could go flat out on full boost with no problem. Investigations found that at high revs, oil was getting centrifuged out of the big ends. This was ok on the bench test twins because they used a main engine oil pump. However with 12 cylinders oil was thrown out faster than the pump could push new oil into the crank. Sooner or later, a big end went pop.

Could high revs and thin oil be an issue with the Boxer 1200? oil gets thrown out faster than the pump can keep up?

 

[cookie]

Why would pressure go up then go up again? Normal pattern is high pressure from cold that drops to a running pressure as the engine warms up.

because the oil reaches the gauge first, then increases as it meets resistance from cam bearing or similar?

 

[JimVonBaden]

Sure, It's just a hypothesis.
It's (generally) accepted that there is some sort of right hand cylinder head issue with 1200's and if we were being scientific about it, the onus is on those proposing the hypothesis to prove or at least advance the understanding of the issue as it relates to their hypothesis.

However back in the real world no-one is going to sacrifice a bunch of 1200's to try and work out what's happening (and BMW sure as hell aren't going to). So, we'll probably never find what the real problem is (assuming there is one).

So, we're going to get these assertions and rebuttals in forums like this and ADV for ever. The people with the theories will stick to them and those rebutting them will stick their fingers in their ears and call bullshit but without evidence it's all just speculation.

However, getting back to the theory in discussion here, it may be complete coincidence that the 'problem' occurs on the high cylinder when the bike is on its sidestand but I'm a big believer in Occam's Razor and without better evidence to say otherwise, I'm prepared to give credence to the theory that the two are related (I may be miss-remembering this, but I'm pretty sure the UK police instructed their bike cops to stop leaving their 1200's idling on their side stands - yes - it doesn't prove anything).

People rebutting the theory bang on about the fact that the lubrication system is high pressure pumped , oil film strength, etc, etc and they're quite right but I don't think the problem is a lubrication issue so none of that matters. My 'theory' is that it's more likely a cooling problem and that the 'high' head may be seeing a reduced cooling oil flow under certain conditions. As the cooling circuit is a separate low pressure, high(er) volume system and doesn't have oil pressure monitoring, we have no way of monitoring cooling flows so my theory is just as impossible to 'prove' as any other

But, I'll stick with starting and riding off (after a few seconds), trying not to idle it to long when hot (and certainly not on *any* stand), using decent semi-synth, heat tolerant oils and continuing with my private quest to work out a way of adding a cooling fan to the oil cooler (been trying to do this since if first got my 1100)

Which makes it the perfect theory, because it can neither be proven or disproven.

Occam's Razor is a nice little theory builder, but it is as silly as your theory with zero proof. If you can neither prove nor disprove a theory you may as well say it is God's fault.

The truth is that so few occurrences of this have happened that it could be postulated that the main bearing is a defective bearing, or batch, or the design of the right side being offset from the left causes the issue, or the oil passage is too small, or... or just bad luck. There is no reason to suspect that the sidestand has anything at all to do with the issue, and it has nothing to do with denial, just common sense and a bit of mechanical knowledge.

Jim :cool

 

[JimVonBaden]

I really can't see how the LHS cam cover on a BMW boxer can hold enough oil to drop the sump level enough to starve the oil pump. If it was that full would there not be oil smoke on starting from oil leaking past the valve stems.

It can't. I've removed the side cover on the side stand a few times and no more than a couple ounces comes out.

600cc pistons and rods have a lot of internal inertia so take a lot of starting and stopping at any speed but at low idle speed they wont be moving smoothly. That clatter can't be good for the crank bearings oil film. How often do we notice a rattle at tickover thats gone when its run a few hundred RPM faster? Do that on a hot engine and expect trouble.

I've recently put an oil pressure gauge on my bike. From cold, at tickover, it shoots around 90psi then after a few seconds goes over 100psi. The pressure is clearly fine but Ive not seen any other engine do that. Why would pressure go up then go up again? Normal pattern is high pressure from cold that drops to a running pressure as the engine warms up. Ive not yet had it hot enough to see what happens with thin oil at tickover.
Edit - maybe its the pressure relief valve popping off as the oil starts to move.

Crank bearing failure could be riding style - hot engine, thin oil low revs, under load breaks the oil film. Slogging an engine is always stressful to the crank and rods. Mine with a power commander will easily pull a high gear at under 2000 revs, but I avoid doing it. Who knows what such slogging could be doing to the crank.

During WW2 Rolls Royce were developing the Crecy 24 litre sleeve valve 2-stroke based on the Merlin layout with the Merlin 2 stage blower. V twin bench tests estimated it would give double the power of a Merlin. But the full size V12 engines would regularly throw a conrod long before they were at full power. The V-twins could go flat out on full boost with no problem. Investigations found that at high revs, oil was getting centrifuged out of the big ends. This was ok on the bench test twins because they used a main engine oil pump. However with 12 cylinders oil was thrown out faster than the pump could push new oil into the crank. Sooner or later, a big end went pop.

Could high revs and thin oil be an issue with the Boxer 1200? oil gets thrown out faster than the pump can keep up?

That is the thing, no one knows what causes the VERY FEW issues, especially in light of the very longevity of the boxer motor, and the very few times the motor is an issue.

Want to worry, worry about the final drive, drive shaft, ABS unit, etc.

Jim :cool

 

[MattW]

Which makes it the perfect theory, because it can neither be proven or disproven.

Occam's Razor is a nice little theory builder, but it is as silly as your theory with zero proof. If you can neither prove nor disprove a theory you may as well say it is God's fault.

FFS I'm not trying to convince anyone else - it's just my theory. I really couldn't care less if you or anyone else subscribes to my theory but I reserve the sodding right to spout the same crap as you or anyone else on this forum.

Your theories and rebuttals are worth the same as mine Jim.

 

[WindyChuffer]

Why would anyone let an engine that relies on air flow for cooling stand still idling? Side stand or centre stand. Seems rather dumb to me.

IIRC the manual says to not do this. Start engine and ride off. Problem solved.

 

[Bendy toy]

Dead right idling causes a lot of internal stress if not on the cranks it does on the cam chain. At speed the system inertia smooths out the valve loading. At tickover each one snatches at the cam chain.

My car says 70k for cam belt. But as an aside it says mostly town use or short journeys 40K. Cam belt life is more or less halved when car is used gently.

Final drive. Oh yes I'm £800 lighter. £350 for FD bearings £150 for drive shaft UJ.. The remainder absorbed by trunnion bearing brake disk and carrier.
I also replaced the (weeping) gearbox output seal, swing arm and had the rusty frame painted. That lot all over and above the FD costs.

 

[WindyChuffer]

...My car says 70k for cam belt. But as an aside it says mostly town use or short journeys 40K. Cam belt life is more or less halved when car is used gently.

Town use / short journeys are not gentle use of an engine...

 

[Bendy toy]

No argument with that but try telly Joe Public. One lady owner never been faster than 40.

 

[JimVonBaden]

FFS I'm not trying to convince anyone else - it's just my theory. I really couldn't care less if you or anyone else subscribes to my theory but I reserve the sodding right to spout the same crap as you or anyone else on this forum.

Your theories and rebuttals are worth the same as mine Jim.

If you are not trying to convince anyone, then why did you even post it, and why argue it?

You are right though, your opinion is worth no more than mine, or anyone else's!

Jim

 

[Magwych]

So here's a few questions:
What is the oil pathway for the high volume/low(ish) pressure cooling feed to the exhaust valves?

Is there single gallery that passes oil to the left and right hand side, each of which then returns to the main sump;
or, does the feed go first the left, ciruclate around h exhaus alve, then pass to the right and finally drain back to the sump ( or vice versa);

Is it the exhaust valve feed or the main pressure feed that branches off the oil cooler, and at what point? Before or after the feed take-off for the RHS exhaust valve? When the oil thermostat opens, is it possible that the RHS valve suffers from a loss of that cooling oil feed ?

 

[Flipfly]

This is epic

IMHO Steve is a very knowledgable guy so I'd heed the warning.

Some of the examples here are brilliant.

The japs don't make boxers, yeah they do, but a Scooby doesn't have a side stand, yeah but a Goldwing does.........erm a Goldwing isn't a boxer engine

The HP2 only came with a side stand.........erm, that wasn't a twin cam engine

From what I understand, Steve has questioned the twin cam and leaving it running on the side stand, all other boxer variants are irrelevant, it is a potential twin cam issue, probably due to the design of the cam covers and the oil feeds to that particular engine.

Personally I have always put my boxers on the centre stand or picked the bike upright before starting, but it's only habit.

The 1150 is the pinnacle of boxer engines btw, all the later variants are ridden by people who make silent farts

 

[Bendy toy]

The Honda Goldwing IS a boxer with two or three cylinders on each side.

The front timing cover has a large oil gallery each side at the top likely to supply the low pressure cooling oil feed. Drainage will be via the cam chain tunnels.

The rocker covers on any variety of BMW boxer are not big enough to drain the sump enough to starve the oil supply. If the either valve cover did does flood, there would be some oil leakage past the valve stems, blue smoke on start and eventual carbon build up on valve stems. Both are very rare on modern BMW boxers.