What would cause this sort of valve damage?

[stinkwheel]

https://i48.photobucket.com/albums/f216/stinkwheel/enfield%20head%20231010/CIMG1283_zpsed913502.jpg
https://i48.photobucket.com/albums/f216/stinkwheel/enfield%20head%20231010/CIMG1279_zps8a3ec2ae.jpg
https://i48.photobucket.com/albums/f216/stinkwheel/enfield%20head%20231010/CIMG1281_zps4cf275ec.jpg

On my Enfield bullet 350 classic (essentially an old aircooled pushrod single). The exhaust valve.

It was all gunked up with hardened carbon deposits which I've removed and this is what's left.

There is a tiny amount of pitting on the valve seat but not enough to worry about.

My main thoughts are either:
1) It's been pinking and I didn't notice (although the plug's ok, biscuit brown on the electrode, no nibbling).

or

2) My hugely excessive oil consumption has left deposits on the edges of the valve which have then battered their way into the metal.

Found out why I was down on compression though!
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Howling TerrorOutOfOffice]

Has a fault by the manufacturer been ruled out or looked into. They look lightly mullered.
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[Walloper]

Soft valve face vs hard valve seat mitt carbon deposits.

Look at new rings too if compression is weak.
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[stinkwheel]

[Walloper]

[Aff]

Running lean causing excessively high exhaust temps?

Or bad valve seals letting oil run down the stem and stick to the valve?
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[CestrianX]

My first thought was fueling but I see you point about the oil. So what's in the oil that could cause that much damage? What oil?

[Kickstart]

Hi

That is quite nibbled away.

Valve clearances a bit tight maybe? With a valve made from a different material the rate of expansion might be different.

All the best

Keith
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[stinkwheel]

There are no valve stem oil seals. This is normal.

I think this may be the thrust of the problem (and is why I tore the engine down in the first place, to fit some aftermarket seals).

It burned 2l of oil on a 350 mile round trip at the weekend.

Clearances SHOULD be ok. It's a zero-clearance tappet. I've never checked them when they're super hot (burned fingers prevent me) but you could still spin the pushrods at the teardown.

EDIT: You know what, When I look closer, the edges of the valve are bent down all the way round. I think this is big lumps of carbon being hammered between the valve and its seat.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Ariel Badger]

To let 2L of oil past the valves the guides must be destroyed, I have never seen oil consumption like that. How are the bore and rings?
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[Nobby the Bastard]

[jimspeed]

It looks like the edges are hammered in that pic as if there has been debris getting between the seat and the valve.
Is the valve hardened for unleaded fuel?.
surely 2ltr of oil couldn't go down the guides alone in 350 miles? we didn't use stem seals on a few of the rally motors and they didn't really use any large amounts of oil (bronze type guides so maybe a tighter fit when hot?) and I would expect to see a build up of thick carbon on the bottom of the stem from it coming down the guides.
is the air filtration ok?
Just had a think and I saw similar on an engine we built in a hurry, the installed height for the valve spring was wrong and was forcing the valve to bounce on the seat at high rpms, could it be a weak valve spring?
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[stinkwheel]

Well. The oil isn't falling out of it because the bike isn't covered in oil and it hardly breathes any oil out, just enough to keep the chain wet. It must be burning it, although it's not particularly smoky and it's not wet-sumping.

It's not particularly creeping past the piston either judging by the marking on the side of it, although I just found the oil control ring was broken. That probably explains the recent increase in oil consumption but it still used WAY too much even before that.

In fact. It used loads of oil with the previous head and both before and after a rebore. It's always used a lot of oil though, It needs topping up every 150 miles or so and always has done. More frequently if there have been a lot of hills.

There was a fair bit of carbon on that valve. You're seeing it after it's been ultrasonically cleaned. Bit of a buildup on the top of the inlet valve too.

I have high volume oil pumps fitted so there may be more oil floating about in the rocker area than usual.

It has an S&B cone air filter. The inlet valve is tip-top and it doesn't have a hardened seat.

By a process of elimination, it's got to be the lack of valve seals causing the oil loss. As long as the valve damage can be attributed to burning excessive oil, my latest tranche of modifications should fix it.

Maybe I just thrash it too much?

EDIT:
The head is a special tuned head. Stronger springs, lighter valves, bronze valve guides, gasflowed ports, the whole nine yards and I've been running it with lightened, balanced rockers but standard cams and pushrods (the valvegear would theoretically cope with much harder cams and lighter pushrods).

EDIT2: Piston was a bit of a mess too. Scoring and nicks round the edges but the bore looks clean as a whistle, no rubs and no major scoring beyond the top ring. I wonder if this is similar damage to that I'm seeing on the valve.
https://i48.photobucket.com/albums/f216/stinkwheel/enfield%20head%20231010/CIMG1289_zpsacae3911.jpg
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Ariel Badger]

Do not bother with the valve seals, they need a touch of oil to run well. The consumption will be down to your broken control ring plus your big oil pump. Can you add an extra crank case vent to a catch bottle?
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[stinkwheel]

[Ariel Badger]

Ariels use a similar system a flow and a return plunger pump to and from an oil tank it does not circulate a vast amount of oil but it works well. You can buy an upgrade to a Morgo geared pump and this whacks a hell of a lot of oil into the cases (and returns it to the tank) but if not well vented do consume a lot of oil. Does your Enfield have shell or roller big ends? I run rollers and was going to upgrade to a Morgo but on advice did not because of talk of oil consumption issues. On a standard set up I spin my crank at 8K PM and have no problems. I was told that I would need extra venting and experience a slight loss of power with so much oil circulating
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[bladerunner]

Looks to me like it could be .....lack of use causing oxide on the valve...or harder seats with soft valves ...impact damage ... The valve and piston show no real signs of over heating.....but lots of carbon build up which would cause issues if not looked after! That kind of carbon build up is not common on low miles motors if used hard! Either way if the seats look good... Change your valves!
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[stinkwheel]

Shell bearings on the crank. Hence why I thought the increased oil flow desireable.

It's also got a pressure bypass valve on the scavenge side to prevent it overloading the pump. This let me fit pressure rather than volume fed rockers. Excess oil pressure is bled off back into the timing chest from the scavenge pump output. It used to produce loads of mayo in the oil tank before I fitted this but it did nothing to reduce consumption.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[YBR Ric]

If you didn't increase the lift pressure on the timing shaft PRV then any excess oil from the supply feed just ends up down in the sump, but only after being spun by the crank web some of which goes up the bore leading to over oiling and greater oil consumption/loss as the oil enters the combustion chamber via the rings which cannot cope.

I found the better option was to block off the crankshaft PRV and use the pump bodies themselves to bleed off excess pressure from larger capacity pumps by fitting a set of low pressure springs and also doubling up on the pump gaskets. Then if pressure becomes too great the bodies temporarily lift and go into idle mode where they continue to oscillate but do not draw oil from the tank. This also has the beneficial advantage of reducing strain on oil pump drive shaft teeth, the known weakness of the original lubrication system. With fully assembled (dry) pumps and shaft fitted into the timing side cover, you should be able to flick the drive shaft teeth with a finger nail and it should spin freely.

A decent non return valve fitted to the engine breather pipe (like those used in diesel fuel lines) will help reduce the mayo problem quite considerably by preventing cold air continually being drawn over any hot oil and oil mist within the breather tube itself.

Oil consumption should not be a problem even when thrashing once you've got the basics right. My (highly) modified 350 would rev to 6,700rpm and never required topping up between 1,500mile oil changes.

[Ariel Badger]

What he says /\
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[Walloper]

High oil consumption is caused by a few things. The wrong oil, the wrong clearances between 'sealed' components ie poor fit, wear or failure. Some Oil control rings wont work if not fitted correctly. A broken control ring will cause massive oil consumption. Valve stem and guide wear not so much unless you do loads of engine braking or have very restricted air inlet. Too small air filter strangling the engine. Worn compression rings which let too much gas to escape increase back pressure which can push oil past between valve stems and guides.
Some engines use oil by design it is regarded as a wear part. This is to simplify machining and or reduce the cost in technology.
Old engines guzzle oil when compared to more modern devices and tuning the same beast only add more.load to the limited engineering.
You could spend a wedge on hammering out a design criterion/flaw. It is doable if you have the time, patience and collateral.
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W-ireless A-rtificial L-ifeform L-imited to O-bservation P-eacekeeping and E-fficient R-epair

[Ariel Badger]

The old Val Page Ariels (1926-31) had no oil control ring. To stop excessive consumption there is a slot in the crankcases for the con rod to pass through rather than a hole. Some riders still find they are burning too much oil even with this baffle in place and fit a control ring to their piston, this is on a standard low volume oil pump, Stinkys combination of high volume pump, lack of ring and lack of baffle is a recipe to drink oil.
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Bikers make great organ donors, get 115 on your licence today.

[Walloper]

[stinkwheel]

[Ariel Badger]

To put your oil consumption into perspective...My old 500cc 1930 Val Page Ariel would need less than a pint of oil every 1000 miles and most of that had leaked out.
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Bikers make great organ donors, get 115 on your licence today.