Stumper - oil mist on head

Anonymous · Jul 29, 2015

Rohan said:
How do you aim for 'neutral' crankcase pressure ??
High pressure combustion gases aren't going to be discouraged much by the slight pressure in the crankcase either ??

New rings = sealing better could mean that the crankcase is pressurized MORE on the downstrokes though,
regardless of ring blowby. Depending on the breathing arrangements.
It was always considered that oil leaks were often from oil being forced out of the cases under pressure.

Not that this possibly has anything to do with the OP question here....

Dear rohan.
Thank you for proofreading my postings.
Perhaps you could consider initiating your own thread with an original subject matter or at very least your interpretation of how Norton Commandos should/could/would work if only...
Ta.

Rohan · Jul 29, 2015

Are we not allowed to have any discussion in YOUR thread, regardless of where the subjects drift ??
Or what is said.
Sounds like some politicians of late....

acadian · Jul 29, 2015

needing said:
Hi acadian.
Re your "...I suspect a lot of these new "mystery" leaks which have appeared have to do with the fresh top end and subsequent increase in engine pressure..."
I'm with hobot on this one: if your top end overhaul included rings then less blowby gases would be able to pass the rings to pressurise the crankcases. I differ in my thinking to some others by aiming for neutral crankcase pressure by having one-way breathing in and out of my engine. Rationale: negative crankcase pressure encourages gases past the rings.
Ta.

Interesting, I always looked at it from the giant syringe metaphor, that well seated rings just keep the gases above or below them put. So you're suggesting I should have less crank pressure on a fresh top end (not disagreeing with you here)? Aside from the weeping crank seal, all has seemed well since the top end rebuild, no smoking, no excessive oil consumption, plugs tuned out properly and look good, oil supply to head is good... The only change I've made was the new XS breather valve, and mounted (I think) too far back near the oil tank.

Rohan · Jul 29, 2015

Remind us again where this new XS breather is plumbed off - in your engine setup ?

acadian · Jul 29, 2015

Rohan said:
Remind us again where this new XS breather is plumbed off - in your engine setup ?

Had it mounted on the oil tank, just fore of the inlet stub. Previously I had the older version of the valve mounted down in front of the rear ISO tube. I've reinstalled the old version closer to the crank outlet, just resting on the primary cover (71), it's now about 4 inches away from the crank outlet.

New version of XS650 valve

Old version

Anonymous · Jul 29, 2015

Hi acadian.
There is no right or wrong here. I simply question the conventional wisdom of a single one-way crankcase breather exit. I also have a one-way inlet at the rocker inlet cover as well as the exit breather. When a vacuum gauge is connected to the inlet tube, the reading shows 2 inHg exists in the crankcases (at 3000rpm). Aside: I then utilise this engine 'vacuum' via a solonoid switch for oil return from the breather circuit.
Rohan is correct that the original 'high pressure oil pass the rocker spindle' problem is not related to this subject. I respond to your breather comment to present another perspective.
Ta.

Rohan · Jul 29, 2015

Where did I say that ?
Me thinketh you quote someone else.

needing said:
Rohan is correct that the original 'high pressure oil pass the rocker spindle' problem is not related to this subject.

At this stage I'm keeping an open mind.
Especially after having been sprayed with high pressure oil from a miniscule cracked high pressure rocker feed pipe - that left no oil on the engine !.

kerinorton · Jul 31, 2015

acadian said:
Traced the leak to the front rocker spindle cap. Thanks for the tips.

Now that I've got the belt set up I've discovered oil weeping past the crank seal (never leaked before), replaced with a new rubberized one, and still weeps once I get off the highway. I replaced the XS650 breather with the new version they're selling, but I think it's not doing the trick (especially with a new top end, and lots of pressure in the crankcase) Going to remount the old one, closer to the engine.

I suspect a lot of these new "mystery" leaks which have appeared have to do with the fresh top end and subsequent increase in engine pressure.

On a plus note, the Maney belt is set up like a treat!

Sounds like my 850 before the pistons blew. I f you have too much crank case compressions, your rings are stuffed and you wont stop the oil leaks. A good test is th ekick over. If it turns over easily, its probably stuffed.

Sorry about that.. But how do I know?

Dereck

acadian · Aug 6, 2015

Oil mist on head squared away, but still weeping oil past primary crank seal. Scavenge rate seems good, and she does not wet sump very much at all. The weeping only occurs after a good highway run. I'll try the JB weld trick to see if that helps, it's a new top end with less than 500 miles on her, she don't smoke and plugs are good.

Stumper - oil mist on head

Anonymous

Guest

Rohan

acadian

Rohan

acadian

Anonymous

Guest

Rohan

kerinorton

acadian

Similar threads