Any ideas please I am burning oil in my WD G3L?

I have a new cylnder(standard bore) and piston (standard) and rings, I have replaced the valve guides and valves and I have the inlet valve oil regulation screw set at 1/6 out.
I noticed some burnt oil weeping between the fins at the head joint so I removed the head . I discovered a significant layer of carbon (burnt oil) on the piston crown on the exhaust valve side about 1/6 inch deep and an pretty oily piston. The piston is clean of carbon adjacent to the inlet valve like its been washed with petrol during the combustion.

The head gasket hasn't blown and the piston rings are ok.

The only route I can think of for the oil is via the ex valve stem but as I have new guides and valves fitted I am proper stumped . I have only ridden the bike 50 to 60 miles max since the rebuild. I am convincing myself now that I have problem with the cylinder head ....help!

You say you have a new cylinder but did you re-bore it when you fitted the new cylinder as you may find that there was some ovality in the bore that is allowing a route for the oil to seep through?

Julian

email (option): 79aust@sky.com

What make were the rings? Some of the rings you buy these days can be appalling a lot of them come in a white packet with made in England on them, but they aren't made in England, they are just packaged here. Another thing, does your bike frequently wet sump? Could it be a residue from this? When you fitted the rings, did you hone the bore? These are just a few ideas

email (option): davmax@ntlworld.com

No I didn't hone or rebore the cylinder just rode it slowly rarely above 35. Cylinder was new old stock barrel , rings were good from Russells and I gapped them. I haven't checked the sump but I didn't think it's wet either. Thanks for all the ideas though.
Is it usually necessary to hone brand new cylinders? I did use some very fine wet and dry when degreasing the cylinder before fitting.

New cylinders are usually honed to size by the factory. Russels do sell some parts that are from spurious sources such as M20 fork links that are Indian made so just because it was from there dosen't mean that it is NOS genuine parts, unless it came in a genuine packet. Hepolite rings are now made in China and I've not heard anything yet about their quality, but they are deliberately packed in old style packaging. I still suspect the rings for the moment

email (option): davmax@ntlworld.com

I have the same trouble with my 16H, an actual deposit of oil on top of the piston. Everything on the engine was replaced and rebuilt. I've finally diagnosed the problem being the conrod having a slight bend or the small end busch being reamed out of true, I'm having it redone right now. It might be worth a quick check, you can tell if there's a problem by looking down the barrel, the piston should track dead center of the bore, if it's bent, it will crowd one side or the other, it will also do a little wobble as it rounds the top and bottom, changing directions. This causes the rings to unseat and oil to come up past them. A twisted rod will have the same results of profuse oil in the combustion chamber. Not saying thats what you have, but the oil on the piston is certainly a symptom of my situation.

Is it usually necessary to hone brand new cylinders? I did use some very fine wet and dry when degreasing the cylinder before fitting.
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Roger,

It's not the cylinder that needs honing, its the barrel bore.
The problem with putting new rings in an old bore is that the old piston rings have worn the bore into a unique fit that over time it seals to suit these rings.
It's always worth getting the bore honed before fitting the new rings to ensure the bore has a perfectly round circumference and isn't (exagerrated) the shape of an egg originated by wear of the old piston rings.
I have a hone that can clean it up if you really get stuck.

Julian

email (option): 79aust@sky.com

During the rebuild I managed to break two compression rings that came with the original piston. The replacement rings (Russell's) had slanted ends the original rings had square ends. I have a mixed the two types of ring as was advised this would not have any adverse effect providing they were correctly gapped. Does anyone beleive I should fit all three with slanted ends?

Roger
Did the bike lay down a smokescreen when you rode it for those fifty or so miles? You don't say in your post but if it's burning as much oil as you indicate it should have. Has the level in the tank dropped? I am also curious how oil can leak between the fins if the head gasket isn't leaking. Where you unaware of a problem until you saw the oil leak?
It sounds bad but may not be as serious as you think. More info needed.

Oil can only get into the cylinder three ways.
1) gets "sucked" in from around the inlet valve guide or from a pool of oil in the inlet tract from a crack in the barrel.
2) gets sucked in through the carb due to a cracked barrel
3) slips past the oil scraper rings.

Now about rings.
Top ring is the fire ring
It's job is to take the heat and compression wave from the igniton & combustion.
Second ring is the prime sealing ring
because it is not directly exposed to the harsh combustion enviroment it can seal better than the top.
Oil scraper.
This ring works backwards to the other two.
It is not forced against the cylinder wall by gas pressure behind it but rather by it's own spring force.
It does not present any resistance to gasses passing from top to bottom.
It prevents oil passing from under the piston up the cylinder wall into the combustion chamber.

On side valves 99% of excessive oil build up will be due to failure of the oil scraper, particularly if it is a one piece cast iron ring as these are highly prone to warping when being fitted and highly prone to breaking when fitting the piston into the barrel.
This is why I always use the 3 piece steel oil scrapers.

As for the bore.
unless you could see pronounced cross hatched honing in the bore even a new barrel needs to be honed

email (option): wariron@tpg.com.au

Another possibility is that the oil that is visible between the cooling fins is actually coming out of your exhaust.
When the engine is stationary this oil is leaking via the exhaust valve stem and accumulates on the exhaust valve (if closed), if you turn around the engine before starting this oil will enter the combustion chamber.
While starting much will be blown out, what is left behind will cause a heavily smoking engine for a short time.
The amount of oil that can leak into the exhaust can be reduced by machining a slot between the oil pocket and the in- or exhaust push rod bore in the rocker box.
At some point this was a factory modification, I think because of this reason.

Regards,
Peter

I have to make a correction to Daves post regarding 'new' Hepolite piston rings. Having spoken to Wassells when this was discussed previously (who now own the Hepolite name and commissioned the parts) I can confirm the 'Hepolite' ring sets are made by Hastings in the USA...As a matter of interest the pistons are not Chinese either...They are made in Taiwan by a manufacturer of OEM pistons for the Japanese car industry and others....
I was told they weren't trying to produce a 'top of the range' and 'top price' piston, rather a good piston at a reasonable price. I have a friend who has fitted a number of sets during engine rebuilds and has had no problems so far...Ian

email (option): ian@wright52.plus.com

That's pleasing to know Ian! Hastings rings are one of the top ring makers for aftermarket HD pistons, hd pistons have been made in Taiwan for years and are not known to give any problems. It would be nice to use them as I've shied away from Wassels usual offerings and the Australian pistons, sometimes to my own detriment as I've flat refused to bore some customers barrels if they came in with the old Wassels ones.

email (option): davmax@ntlworld.com

Took the head off again and I think I may have found the problem.

There is small hole in the head casting oil channel that feeds the valve guide from the small oil hole in the head by the push rod tubes. The inlet valve has a similar channel but externally the oil feed adjustment screw exists. On the exhaust side no screw just a flat face. The top of the new exhaust valve guide is covered in burnt blackened oil and the valve stem itself has evidence of burnt oil down its entire length. It looks like the valve is being oversupplied with oil from the mysterious tiny hole in the head-casting adjacent to the guide?

Conveniently I have another head and when comparing the two there is no hole in the same place so it looks like over oiling from the new hole is resulting in excessive oil down the valve guide and onto the piston.

I wil rebuild it using the replacement head and see if the problem goes away.

Cheers

New head has fixed my problem

Done about 50 miles with the new head original valves and no more oil where it shouldn't be. Still no wiser as to what caused it especially as I had new valves and guides fitted to it.

When I stripped the old head there was a lot of burnt oil around the top of ex valve and signs of burnt oil down the valve stem. Any way all seems in order now so happy days especially as summer has arrived! Thanks for the ideas.

No one mentioned wet sumping?