Lots of white smoke - W/NG

[stevewhitt]

Evening all,
I took a working w/ng and now have a non-working w/ng!
On my journey I replaced the carb with a rebuilt 276. I also replaced the head with a head that I have been building up over the last year; the new head has new valve guides, valves and springs. All lapped in and sealing well as far as I can tell.

I Had to remove the barrel and I confess to having slightly damaged the skirt of the piston when refitting, but I rubbed down the burr and it seemed to be OK.

I also fitted a copper washer on top of the barrel spigot as it has never been a gas tight seal with the head.

All put back together and its obvious that she is burning oil; tons of white smoke, an oily residue making its way through the exhaust and spitting of the same residue out of the spigot/exhaust pipe interface. Very oily spark plug.

So, I stripped her back down again and can't see why there is a problem; no broken rings, no scouring of the barrel bore, top end all looks as it should.

My first assumption is that white smoke is down to burning oil, and nothing to do with carb settings - is that a reasonably safe assumption?

If yes, what should I check next?

All help and suggestions gratefully received.

And before someone says it, I am aware of the old adage, 'if it ain't broke, don't fix it'.

[will_curry]

Has the scavenge side of the oil pump stopped working?

[stevewhitt]

Oil is flowing nicely.

[stevewhitt]

Although it did seem to take an age to start flowing, but once it started, it has been regular.

[stevewhitt]

It is an interesting thought though Will. I also converted the bike to tin chain guards along with fitting the correct tin timing cover, for which I had to make my own gasket. I think I was quite careful in making sure no holes were blocked by the new gasket, but you never know. Are there any obvious oil ways close to the gasket that I need to be aware of?

[will_curry]

I don't think there are any oilways that might be obscured by the timing cover gasket . . .

Presumably this problem only started after you rebuilt the top end and it was running
well - leaky cylinder head joint not withstanding - before you stripped it.

W/NG engines in original order used the small oil pump of the time and fitting the later,
larger pumps can cause issues.

As ever, some pictures may well be helpful.

[stevewhitt]

Slipped the timing cover off, and I have attached a picture which shows an oil way which may have been partially covered by the gasket Will. Its impossible to be 100% sure, but I am 75% sure it was at least 30% covered by the gasket.
I used a thick paper gasket, with wellseal and that stuff tends to run....

If the hole I have shown was partially obscured, do you think that would cause the issue?

[stevewhitt]

I had a nagging doubt about the gasket and oil ways, which I ignored and forgot about Will. I think you may be onto something.

To answer your other questions:
Presumably this problem only started after you rebuilt the top end and it was running
well - leaky cylinder head joint not withstanding - before you stripped it. - Yes, ran very well.

W/NG engines in original order used the small oil pump of the time and fitting the later,
larger pumps can cause issues. I think mine is original.

[will_curry]

The hole to the left of the left side of the pump is the drain for the
timing case. I wouldn't think that drain being partially blocked would
cause oil to get into the combustion chamber.

I can't remember what the diameter of the original delivery plunger
was for the W/NG but if you look on Draganfly's website I think there
is some useful information.

I wonder if oil is accumulating in the rocker boxes and then making its
way down the valve guides?

[stevewhitt]

I spoke to the engineer who fitted the new valve guides today, and that is what he wondered as well. Why would oil accumulate in the rocker boxes? When I removed them today, there was an accumulation of oil at the bottom of one of them.

I can check the oil pump but that is a part that was working and has not been disturbed.