Smoking cylinder

So with the Googling I have done quite a popular subject. The right cylinder smokes. I had the head off over the winter, everything looked okay but I replaced valve seal and head gasket. Put it back together bike ran okay for about 50 miles then turned into a 375cc bike.
So took the head off again and found the valve seal had split. However mug of tea in hand I spent a bit of time looking at the head round the valve seal. I have a thin metal washer that the valve Spring cup washer sits on and there is like minimal allowance for oil to get past and into the drain hole in the head and down the barrel.
Looking at the parts catalogue there perhaps should be a thicker heat resistant washer that creates more of a gap for the oil to pass.
My plan is to drill some holes in the cup washer, line one hole up with the drain hole as I think that the area around the right inlet valve is essentially flooding with oil and it is proving too much for the valve seal.
Good compression, done the remove head oil line and run it thing, valve guides are tight, valve stem in spec, doesn't wet sump, barrel and head mating surfaces are flat, left cylinder could win a beauty competition on nice combustion.
Anyone think not a good course of action, or will the cup washer break up?

I don’t know if the cup washer will break or not, I imagine that will be determined by how carefully you drill, and dress afterwards.

But lining up one of your holes with the drain hole won’t work as these things fret and rotate in use.

I would suggest a more careful study of the parts manual, you sound like you may have identified a cause, but modifications as you suggest shouldn’t be necessary if you’ve got the correct parts in place.

Thanks, it's a Combat engine, I have a feeling that with the 2S cam there were only heat insulators under the exhaust valve springs. I was thinking also that any hole that started lined up would not stay that way for long, hence I thought to drill more than one.

I take it the rocker spindles are in the right way up and are not loose?
Try pouring a bit of oil down the hole it maybe an optical illusion,and keep in mind that hot oil will be even runnier,
You could always open the entrance to the hole slightly with a dremel or similar I have done this on my commando it probably didn't need it but I can't leave anything alone!!

The spindle flats face out from Centre of head and are snug.
When back at it was going to check the barrel oil way was clear down into the cases. However good idea with oil. Will experiment washers in place and pressed down, plug valve guide, pour a little ATF and see if it flows past and out of hole in head/barrel interface. Not sure about Dremel but will think it through.

I seem to recall reading that the combat motors did NOT have washers under the springs. Per what I remember, they were intentionally not installed to reduce the possibility of coil bind. If I remember this correctly, that was a horrible way to accomplish that. But it was cheaper than for Norton to obtain different valve springs! And as far as longevity, well, the Combat engines blew up long before the valve springs could have eaten their way into the head!

I agree with the others re the oil draining. It does look bad as far as the tiny hole but it works. I did a lot of checking of oil drainage some years back and unless the drain hole is obstructed by gasket sealer OR the spindles are installed facing the wrong way, the head drains just fine. Mods aren't necessary.

FWIW, oil entering the combustion chamber via a valve seal/guide may smoke a lot but it won't turn the engine into a single cylinder engine. If one cylinder is cutting out, it's probably an ignition issue - plug/wire/coil, etc

first thing i would look at is if the top of the valve guide and bottom of the retainer is hitting at full valve lift when you stated you found the seal split. the washer IE shim does not belong there on a combat head as from factory and if the OD is to large it can cause coil bind but that is another issue. we need more info as to was anything done before this problem started like valve guides replaced.

Steves said:

So took the head off again and found the valve seal had split. However mug of tea in hand I spent a bit of time looking at the head round the valve seal. I have a thin metal washer that the valve Spring cup washer sits on

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Thanks Bill, I think the valve geometry is good, will check again though. The left side is identical and trouble free. The shim is very thin, I assume to try and give enough space to let oil flow under the bucket washer. The drain hole is pretty much covered by the bucket washer which looks a perfect fit in the cylinder head recess. Spring sits in the bucket washer and looks a good fit, everything turns over nice. I know this might change at high revs due dynamics, momentum etc.

Mike I did consider an ignition problem on the premise that the suspected cause of a problem is inversely proportional to the actual cause. Nice fat sparks, actually been running one grade hotter plug on the dodgy cylinder.

I'd preface my comment with I have very little practical knowledge of Norton motors! but I'll tell you my story!

How many miles on the bore? Original or re-bored? What pistons/rings are you running?

I had a problem with a cylinder smoking, did all the things you did, replaced valve seals, I got the head rebuilt.

I had fantastic compression & I did a leak down test & everything seemed fine.

The lads on this forum were extremly helpful & were puzzled by my apparent healthy engine but I had a cylinder that had oil burning, lots of smoke, messing up plugs etc.

Eventually the consensus was remove the barrels, which was something I was avoiding doing, all my logic was telling me it was something else!

Boy was I happy (and sad!) that I took the barrels off, my pistons were in a sorry state, signs of the piston skirt rubbing the cylinder wall. You stated "done the remove head oil line and run it thing" If the cylinder kept smoking after a quick spin this would tend to discount the top end! (although some posters on my issue said the smoke could be coming from the silencer soaked in oil! BUT putting in a new plug would discout this theory, if there was fresh oil on plug etc.)

You also state "left cylinder could win a beauty competition on nice combustion" is this comment based on the visual inspection of the bore or based on the compression test? or both? Just trying to see if the bore has any signs of the piston touching?

With my bike it looks like the top ring and maybe the 2nd ring was sealing against the bore but the oil ring was not, hence the oil in the bore but I had good compression.

The barrels are with Jim C. for some TLC, he hasen't inspected them yet but it might have been the bore was too tight for the pistons. I had about 5K miles on the bore, I think I originally stated 14K, I got mixed up with another bike!!

I hope it's not the bore/piston issue but as was stated to me it's not that much hassle to take the barrels off & inspect them and the rings/pistons etc. I avoided doing this for a long time chasing dragons that didn't exist!

The great thing is, everything can be fixed with some time & money

Thanks Click I appreciate you sharing that. The oil line off produced less smoke so as you know intimates a problem in the top end. I need to spend more time inspecting the bores (after work today) but a cursory look everything was okay, still had honing marks after 10k miles.

Steves said:

Thanks Click I appreciate you sharing that. The oil line off produced less smoke so as you know intimates a problem in the top end. I need to spend more time inspecting the bores (after work today) but a cursory look everything was okay, still had honing marks after 10k miles.

Click to expand...

Great, thankfully doesn’t sound like the hassle I had. Best of luck tracking down the culprit

Steves said:

Mike I did consider an ignition problem on the premise that the suspected cause of a problem is inversely proportional to the actual cause. Nice fat sparks, actually been running one grade hotter plug on the dodgy cylinder.

Click to expand...

One thing to consider - as you know, a good spark with the plug sitting out on the head just means there's a good spark with the plug sitting out on the head! Under load, dodgy ignition components, especially in the secondary, may become intermittent/fail even though they work fine under low-load conditions.

MexicoMike you get the whole enchilada. I took head and barrels off looked everything over scratched my head and checked the coils. Yep duff coil, back together new coils running like a train, just in time for spring/summer, which by the way is taking its time in getting here in the UK.
Funny thing isn't it, there being an inverse proportionality in perception between actual and perceived tech problems........aleast in my world.

Steve, what was your final conclusion with the thin metal washers blocking the oil hole scenario?

Well I went ahead and drilled 4 holes in the washer, a 5th hole through my thumb nail when the first drill bit broke, I was thinking at the time my methodology would not pass a H&S audit. I think the washer is heavy duty enough so that its strength is not compromised. I played around with filling the valve area up with ATF and came to an unscientific conclusion it flowed quicker.

Well that's a new one.

I always thought if you think you have a carburation problem, it's probably electrical and when you think you have an electrical problem, it's probably carburation. Now if we think we have an oiling problem it's probably an electrical problem.

i had a hate relationship with the electrical on a Norton... thats why the only remaining lucas item on the bike should be the headlight shell....