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My 78 3 1/2 recently started to see more and more oil flow through breather tube on the top of the valve covers. I am suspecting possible valve guide wear. Any other thoughts on the matter, the bike has ~11k miles (18k KM) I have not been able to find any threads on the list pertaining to head problems hence my question.

My 350 had 48000km when i got it, then i got a converter to MPH on the speedo drive and now it shows 70,000, which is about half the mileage of my other 2 bikes. I have recently fitted new pistons,all bearings except small ends and ground in the valves very lightly, and the seats were by no means rough.The one thing i have not had is excessive oil, via the breathers. if you've only 11,000 miles, what I wonder is whether water+oil vapour is what's coming through.Is the oil volume 2.5L or 3L? Has the bike been on a good blast lately?
Best of luck.
john

Oil goes down worn valve guides, not up them.

Crankcase pressure is what will drive oil up to the heads. That's why there are labyrinths in the main breather, to separate oil and provide enough back pressure to drive oil mist to the valve gear.

Check that your main breather isn't blocked or restricted.

That was one of the symptoms of a broken piston ring on mine - the top one as far as i remember -Duncan

Breather tube and labyrinth are clear. Will get her down off the lift and take her for a spin to metaphorically blow the cobwebs out and see if the problem persists. On the matter of a broken piston ring (eeek), wouldn't I see issues with compression? I tested compression very early on and have ~130 psi in each cylinder. THANK YOU to all responding to the thread.

I had excessive oil coming from the main breather (not rocker covers) when the engine was hot so I added an oil catch can & now the problem has gone away.
Still have separator fitted & using a K&N vent filter on the exhaust of the catch can.

guzzirunner wrote:Breather tube and labyrinth are clear. Will get her down off the lift and take her for a spin to metaphorically blow the cobwebs out and see if the problem persists. On the matter of a broken piston ring (eeek), wouldn't I see issues with compression? I tested compression very early on and have ~130 psi in each cylinder. THANK YOU to all responding to the thread.

I'm not an expert on the Morini engine, but in general most engine layouts (there are exceptions) create air movement in and out of the crankcase as the pistons go up and down, hence the need for a fairly large crankcase breather. As already said, that is the first thing to check, because something is sending an excess of air out through the rocker box breather, carrying oil droplets with it. i.e. it looks as if it's breathing via the push rod tubes. Valve guides do wear, but the effect is usually noticed in excess oil consumption as oil is sucked down the inlet valve guides. I don't think there is much oil movement one way or the other in the exhaust valve guides, even if really sloppy. If there is excessive crankcase pressure, in my experience it is usually caused by blow-by, either via worn bores or one or more broken piston rings. A less common possibility is a damaged head gasket allowing pressure to leak into oil ways or push rod tubes, very much depending on the design of the engine - not sure in the Morini case. I must say though, a blown head gasket usually finds its way out to the outside world pdq!

To answer your question, broken rings, etc can give you low compression readings, but it's not always a reliable indicator because the oil can help seal it well enough when the engine isn't actually running, just cranking. Again in my experience, low compression is usually due to valves not seating for some reason.

To end on a more optimistic note, there is usually some kind of baffle to discourage oil from going up the rocker box breather - worth checking that that is in place? Apologies, again I'm not sure in the Morini case. Also, I'm not sure if an over-filled crankcase can lead to excess oil upstairs in the rocker box - worth checking that as well? One thing I do know about these engines is that they are generally reliable up to high mileages, so the scary scenarios of broken rings, knackered bores and so on don't sound very likely, especially if it isn't smoking.
Good luck with it!

Just for reference regarding compression's on a 3 1/2 Strada, I'm getting 160psi on the front & 155psi on the rear, so I would have thought 130psi maybe getting toward the low side. I don't have an absolute minimum running compression to go by.
Carry out compressions & get a reading then add some oil down the spark plug hole & do the compressions again, if the result is a major difference from the pre-oiling then its rings.
Forgot to mention that the compressions were done using kick start & not the starter motor, figures maybe a little higher with the starter.

TurboRestorer wrote:Just for reference regarding compression's on a 3 1/2 Strada, I'm getting 160psi on the front & 155psi on the rear, so I would have thought 130psi maybe getting toward the low side. I don't have an absolute minimum running compression to go by.
Carry out compressions & get a reading then add some oil down the spark plug hole & do the compressions again, if the result is a major difference from the pre-oiling then its rings.

Just checked mine and I get 180psi on both pots, maybe a fraction less on the rear. Does this mean I've found something on this bike which is not broken? Woo hoo!

Update:
Performed a leak down test both cylinders. 100 psi in / 94.5 maintained pressure both cylinders. At least I am more confident that it is nothing major. Crank breather circuit clear.......I am going to pop the rocker covers off and double check to make sure the breather valve is not stuck in any way. I really thought 130 psi compression was considered ok (at least for the mileage). Thanks for all the input from everyone. Still scratching my head a little but will find the problem. Happy riding season!

EVguru wrote: Crankcase pressure is what will drive oil up to the heads. That's why there are labyrinths in the main breather, to separate oil and provide enough back pressure to drive oil mist to the valve gear.

Check that your main breather isn't blocked or restricted.

Paul, are you sure that the labyrinths in the main breather tube are responsable for the right pressure in the motor? The normal tubes have a inner diameter of 18-19 mm. The labyrinths reduce them to less than the half of ist. The bore in the crankcase for the respiracion pipe is only 6 mm. So I don´t think that the labyrinths are decisive for the pressure (guess they only shall retain the oil). But they can be a problem blocking up the tube, because there normaly are two of them. If they are in a wrong position towards one another they can block up the tube. I have only one labyrinth in my tube that reaches to the end of the bike, and there is only very little oil fog coming out after hours of good rides.

norbert

ok...rocker cover shows no signs of problems. Put a bore scope down both cylinders (yes I have access to cool toys). With pistons at BDC no signs of scoring of any kind. Cylinder walls shine so well you can see the reflection of the top of the piston. Back piston looks great. Top surface of front piston has a little bit of carbon deposit but not bad.

Hi what oil are you using? Peerhaps change it and see if that cuts the mist.

When I first got my Morini I replaced the breather for some black pipe and didnt have the labyrynths in. A few years later I bought 2 and put them in a new piece of clear pipe. Noticed straight away that the engine felt stronger. My bike has 45000 kms on it and doesnt use any oil . The main breather seems to be pretty clear . Your bike has low mileage
so try an oil change to see if that helps.

Ideas from an old engine guy :

1- Too much oil in the engine

2- Too much Crankcase pressure

3- Too high engine operating temperature

4- Any combination of the above ......

Note: operating temperature is often overlooked,,, when oil get very hot it cooks away.....

Robert in California