A Series Crank Case Breather

[jhg1958]

I would be worried about forgetting to remove the plug when setting off. With a geared pump it should be able to pull down a vacuum although with BSA tolerances that may not be a problem.

Would a new pump (eg SRM) stop the wet sumping?

John

[muskrat]

G'day John.
It did on my 51 A7.
Now my Cafe is wet sumping and it has roller conversion. I don't want to drill holes in an SRM pump.
Cheers

[limeyrob]

Have you tried riding it every few days? This is what people used to do and it worked!

[muskrat]

G'day Rob.
Since my back fusion and my hip going west I haven't been able to fold myself up enough to get on her. I've had a new hip and modified her (std bars & footpegs + other things) to make her rideable again.
Won't be long now.
Cheers

[limeyrob]

I must say that bike looks gorgeous!  That really needs a good run

[Swarfcut]

    I did say add a reminder for next time, the same goes for on/off tap in the supply line. Draindown will always occur to some degree, on all new rebuilds, new pump etc you may be lucky, but for the rest of us with original balls and springs, porous cases, you name it, we've been there. The feed side was probably only truly hermetically sealed the day it was made.

 Ridden every day, sure, no big deal, dad set off for work with a bit of blue smoke, but left for a couple of months, tank will empty dripwise and it's out with the spanners, sump plate off, catch the oil, recycle.

 My thought was that by preventing air entering the tank, a partial vacuum would reduce outflow under gravity, and save some start up hassle and mess.

 Reckon bergs need a good sealing washer on that oiltank cap, fibre washer 67-42 should do it, same as primary case oil cap. Triumph rocker caps and washers also fit....Unless he's got a cap with a hole and a non standard tank with no breather. " Whittle a bung, bergs."

 Swarfy.

[limeyrob]

I seem to recall it would need a few weeks to come a real problem, by that I mean 1/2 or more of the oil in the engine.  I've always put up with it thinking that the alternative of a tap in the oil line is just too risky.  A bit like riding off with the side stand down or the petrol taps off; what idiot would ever do that...err me.
It would be possible to put a vacuum operated valve like the japanese petrol taps in but its another failure point.

[berger]

Swarfy i was thinking back to when mine had the original oil tank 40 odd years ago and i got oil mist around the tank filler cap, maybe that was in need of a new seal. at present i am one of the lucky ones who has a dance around the garage when i take the screwed cap off the ally oil tank and the oil is there at the same level after 2 or 3 months of winter lay up

[Swarfcut]

 Recent post from a new member ticks all the boxes for every problem possible with a worn engine. Excess oil in the combustion chambers is down to worn bores, pistons and ring problems (broken, worn or the wrong ones), oil coming down worn valve guides, along with too much oil in the sump......it is a so called dry sump system, oil in the tank, not in the sump.

     Oil in the sump, (our old friend wet sumping) due to draindown from the tank or failure to scavenge will result in oil from the breather outlet and increased crankcase pressure venting oil where it can, into the primary case as an example. Running with a rocker cover removed, a bit like taking the oil cap of an old Ford Crossflow, to see how much pressure there is. With piston blow by there will be pressure and combustion smoke, an indication of bore and piston problems.

 So valve guides, pistons, rings, bores and scavenge side along with the pick up pipe and its little ball valve all need cleaning and close inspection. Anti wet sump valve in the crankcase likes an occasional blow through with carb cleaner. All easy things to do with the engine in bits.

  Posted here as a general summary, there is enough on the Forum about every aspect of the system, and in general the faults and causes of trouble are easy to spot.

 Swarfy.

[CheeserBeezer]

Obviously this is a well-worn thread (excuse the pun). A previous poster had a big problems with this and found that the cure was to change the filter screen in the sump. Presumably, a pattern filter screen had mesh which was too fine and wasn't allowing the oil to drain into the bottom of the sump quickly enough. Another problem, which I don't think has been mentioned in this most recent thread, is leaks in the pickup tube. I've heard of tubes which have rust pin holes and also tubes which aren't a good fit in the crankcase half, so the pump sucks air until the oil level covers the leaky part of the tube which means the bike is running with too much oil in the sump.

[orabanda]

Great point about the integrity of the sealing of the pick-up tube.
The tube often cops knocks when the crankcase is handled (dropped / placed on work bench, washed, etc) because it protrudes below the sump plate mounting surface.
This is a reason that sometimes the pickup doesn't align with the hole in the mesh screen.
So, oil can leak into the sump from above the ball in the bottom of the pick-up tube if the tube has loosened into the crankcase, or the alloy has cracked, or the steel tube has fractured, or the brazing has failed between the steel "holder" of the ball, and the tube.
Another issue I had, involved the steel pin riveted into the holder, above the ball, to prevent the ball moving north up the pipe.
The pin was not sealing in the holder, beneath the riveted ends. I silver soldered each end, and yippee, wet sumping reduced, and the return oil flow improved.


To identify any of these issues, even on an engine still in the bike, remove the oil pump and blow compressed air into the drilling that connects to the pickup in the sump.

The sump plate needs to be removed. Wear safety glasses before sticking your noggin under the sump. If the ball and the tube, riveted pin, etc are sealing perfectly, no air leakage will occur.

Holding an air gun with a rubber tipped nozzle into the port will work.
I have machined a blanking plate to replace the oil pump, with a fitting over the scavenge pump port to connect the air line; makes this an easy one person process.

These checks should be done during every rebuild.

If you make a blanking plate which an air hose can be connected to, then the crankcase half can be immersed in water which is a good test for leakage paths.

Basic fettling, but worthwhile.

Cheers,
Richard