Oil being forced from breather

[Andy Williams]

Good morning, towards the end of last year my Super Rocket started to become difficult to start when hot. After trying various things I opted for a mag rebuild. I entrusted the removal and re-instillation of the Magneto to a someone who is extremely experienced in maintaining this kind of bike.
Unfortunately for various reasons including ill health and a house move the work took a long time but when it was eventually completed i collected a bike that fired up instantly hot or cold. Now this is where my troubles began after arriving home i found the rear wheel covered in oil that an investigation showed was being forced from the engine breather on the left side of the engine. I know the old girl suffers from wet sumping which normally shows itself with much smoke on start up (if i haven't used the biked for a few weeks). There was no smoke when startling up when the bike when collected with leaves me to believe the sump had been drained prior to me collecting the bike.
The engine condition is to the best of my knowledge really good with excellent compression and no oil leaks.
I removed the sump to ensure that there was no excessive oil but after reinstalling and starting its still pushing oil from the breather.
The oil return to the tank is excellent with a strong flow.
I have noted that I can feel air pressure "pulsing" from the breather along with the oil. i am assuming that if the ball in the sump pick up was stuck then i would not be getting a strong return to the tank is this correct? could the pressure release valve on the front on the right side crank case be causing this? Finally if the fault lies with the corks in the timed breather would i still be able to feel the "air" pulsing from the breather?
thanks for looking and hope someone can help!

[limeyrob]

Before going deeper I would suggest a jet wash and a run to see if this is a recurrent problem or a one off.  The timed breather is pretty simple and there's quite a bit of leeway on the cork washer before it looses drive, and even then the oil would not come out the breather hole.  If there's crank case compression you really need to do a compression test but it sounds like there is enough compression for easy starting.  If I recall correctly the timed breather pick is quite high in the engine so even with blow but I wouldn't expect much oil, more mist.
My inclination is wet sumping and a one off problem but only another run will tell.

[Andy Williams]

Very many thanks for your prompt response!
 I have cleaned the old girl off and tried another run 3 times now in the hope that the fault will miraculously disappear in vain unfortunately. 
As previously stated I have removed the sump to ensure that wet sumping is not the issue, and gone for a run immediately after with no change.
i am beginning to wounder if the oil being returned to the tank is actually excessive and that possibly there is being too much oil being supplied to the crank cases in the 1st place but dont know if this is possible and if so what could cause it?

[limeyrob]

OK, check out the thread on here "baffled confused and covered in oil".  Its a long discussion because its baffled us all  (well except for one person who nailed it early on..) .  Worth a read, could be your issue.  The sump gauze does not pass enough oil and the level builds up.  If you have the flat bolt in gauze try a run with it out.

[Andy Williams]

Again many thanks, will have a good read in a moment but would not the fact that i have a really good return to the tank rule this out?

[limeyrob]

That's what we thought, but the discussion is very interesting.  What oil are you using and do you have the original domed gauze or the aftermarket flat one?

[Andy Williams]

Im using Comma Classic 20 50 at the moment, if memory serves me its a flat gauze filter.
Seems really strange that all was well (oil wise) until the bike was off the road for about 3 months?
think will take off the sump again completely drain clean gauze and re-check the ball and keep finger crossed! 

[Swarfcut]

 A clue to the problem is what happens to the oil level in the tank. After a run the level should be more or less the same as when you set off, assuming on start up there was time allowed for the pump to scavenge any oil drained down into the sump on standing.

 A constantly falling level shows oil accumulating in the sump, which is then vented via the breather. Just wondering whether all the bits you sent off were the same ones that came back.....

 Try starting from scratch, sump plate off, crankcase empty, oiltank drained, refilled with recommended capacity. Some folks top up the tank, not realising all the oil is hiding in the crankcase.  It's a dry sump system, not like your more modern bikes. The rocker feed is one culprit, too much oil bled off means less going back to the tank, more in the sump, eventually overwhelming the scavenge capacity.

 Swarfy.

[limeyrob]

Yes, I have a cartridge filter in the return and one issue I've found is that it smooths the return flow. So whereas without a return filter the return flow is obviously intermittent once the scavenge pump as cleared any surplus, with the filter its continuous but frothy so the filter must be breaking up the bubbles.  This makes it much harder to see what's going on.

[Andy Williams]

I'm still really confused must of the advice points to poor scavenging and poor return resulting in excess oil in the crank cases. My return is very strong seems almost too much it really is returning under pressure it is leaving the return pipe and hitting the opposite side of the tank under pressure! As the return side of the pump has a higher capacity than the feed can't work out how this is possible? Sump is off will allow it to drain overnight and try again tomorrow. The ball seems to be free can easily ouch it up?

[muskrat]

G'day Andy 
As Rob mentioned check out https://www.a7a10.net/forum/index.php?topic=14612.0 It's a long thread 13 pages so sit back with your favourite beverage. It lists many causes for your problem. Just strange only started after a magneto refurb.
The PVR (pressure release valve) wouldn't be a cause as any blow off still ends in the sump and the scavenge side of the pump delivers more volume than the pressure side.
Now get over to Intro's and give us your story (credit card details etc).
Cheers
edit: Just saw your last post. The return should be strong but after a minute or so should turn into spurts or at least bubbles in the stream.
Have you spoken to the fella that did the work on your bike?

[limeyrob]

Good call about asking the fella who did the work.  I've known some absolutely baffling problems caused by someone trying to be helpful and doing an extra bit of work and not mentioning it.  It happened to me once, I got a car back from some paint work and the bulb failure light was on. I tried everything and swapped all the bulbs (or so I thought). In the end I rang the guy and he said, "oh yes, I noticed one of your number plate lights was out so I popped one in". He'd put in the wrong wattage but it looked the same as the correct one.

[KiwiGF]

How long was the bike left unused? I’m wondering if the rings are stuck and a compression test should reveal that, the bypass gases could cause the breather to “work harder”, a related possibility is the crankshaft oil seal has popped out, easily tested by removing the primary case filler plug.

My thinking is check “whats changed” rather than go through the “baffled” thread but that thread does have a comprehensive list of possible causes….

[Andy Williams]

Very many thanks for all the reply's and advice.
Unfortunately due to a house move and family illness the chap who did the work is unfortunately very much under the radar at the moment so no help from that direction.
The bike was off the road for about 3 months in between mag removal rebuild and re installation in which time i am sure the entire oil tank contents would have found their way into the sump so I'm sure it would have been drained prior to 1st start up after the mag work and before i collected it. 
For information she has an SRM sump plate with the built in drain plug.
Obviously stuck rings is a possibility but although unscientific the comprehension feels fine and she starts and runs fine no smoke or any other indication that something is wrong.
I keep coming back to the amount of oil being returned and the pressure it is returning at, even after a run when i would have though wet sumping in not possible the flow rate seems to me to be possible excessive indication too much oil being fed to the engine but who is this possible?
thanks again.

[KiwiGF]

Going back to your first post and whats come out the breather (pipe) on the engine….the aim of the timed breather is to cause a vacuum in the cases, on start up the gases are pushed out of the breather pipe on the left hand case but this will reduce as a vacuum gets established, an equilibrium will occur where the gases that bypass the pistons will equal the volume of gases exiting the breather pipe (noting some engines just have a hole and no pipe).

My bike does not smoke when wet sumped, or pump oil out of the breather, but others do apparently, but I don’t for 100% know why as the timed breather is quite high up in the case, I guess so much oil gets flung about that some gets through the timed breather and into the internal breather passages in the cases.

Have you changed the oil since the bike was returned? I ask as if oil was drained then I would not put it back, but would fill with new oil, and maybe the wrong oil was used? 

The classic error of course is to top the oil tank up, when 1/2 the oil is actually in the sump, which results in oil everywhere!