Found a reason for occasional but persistent oil return failure

[Steverat]

Josef’s bike has got into the habit of dumping a load of oil on the road and failing to return to the tank- only intermittently but badly enough to empty the tank. I think and hope I’ve found the cause - the little non-return valve in the sump pickup jams shut from time to time. Anyone else seen this problem?

[Angus]

A much later bike but I am sort of hoping that is the cause on my 1960 A10. See my 'where has the oil gone' thread here https://www.a7a10.net/forum/index.php?topic=13251.msg106487#msg106487. I am about to try her again, but if that is the cause what is the cure.

[Topdad]

Wiser heads than mine will help shortly but do either of you guys have a magnetic sump plug fitted as they have been the cause of this problem before if you've fitted the plug nearest to the pickup , worth a check .

[RichardL]

I could envision some kind of crud (maybe very old) between ball and sidewall of tube jamming the ball with only suction applied, but appearing free when pushed by hand.

Richard L.

[Angus]

I have magnetic sump plug. Its been there since I bought her 4+ years ago. Its not the normal one as it in the centre of the sump plate so should not cause the problem and has not until last august and last week. It may not be this, I have given it a good clean and am just setting up to run a test with the sump pate off and a pipe extending the scavenge into a jar of oil. If the oil drains as I expect I will put her back on the road and monitor the situation.

[chaterlea25]

Hi All,
I would try to see if the ball has become magnetised ?
Try and find a small piece of steel that is not magnetised, see will some steel filings stick to it to check (Make sure to clean it afterwards)
Then see will this piece of steel stick to the ball or pickup pipe

If you find the pickup or ball is magnetic then next question is how to demagnetise it

John

[mugwump]

 I  am told that passing an AC current through the item will de-magnetize it. Don't ask me how! Alternatively a de-magnetizer can be got from that well known  auction site on line.

[duTch]

 

........... I have given it a good clean and am just setting up to run a test with the sump pate off and a pipe extending the scavenge into a jar of oil. If the oil drains as I expect.......

 I understand what you want to do and expect it offset so as to not catch any from the sump in the jar, but why have oil in the jar? Wouldn't an empty jar be better ?

 I also can't see that the scavenge pipe wold dump any more than what is in it alone, which isn't much anyway.... the way I see it, a sticky ball allowing any bleed-down would only reduce the potential self-primed action and try to suck air which I doubt...

 Best way I can think of is to pull the pump off and blow air down the scavenge hole

** Edit; having just read Bergs's post (20sec after mine), also run some solvent down from the top a couple of times before/during/after the air  b

[berger]

 I have not been to the pub! haha i can't resist this answer I demagnetise things that shouldn't be magnetic by bashing them about and giving them some hammer on a more serious note its a long time since I had to play with my ball , but once pushed up is there enough room to try and clean it out a bit with petrol and a well made  artists brush or something like that

[Greybeard]

I think we can take it as read that Steve has cleaned all parts of that engine.

[Swarfcut]

   If the ball is found to be magnetic,it is worth trying a little heat to upset the magnetic domains within the metal. Not too much heat, the ball housing is brazed to the pick up pipe, so a hot air gun would be a good start.

 This will also melt any hard deposits lining the housing.

 An alternative thought is that with new, thick oil and a new Super Suck Pump the ball is being drawn to the top of the housing, blocking the pipe, then innocently dropping back down by the time the motor has cooled and the sump plate is off. There needs to be space around the ball for the oil to get by. So a crud lined housing could be the problem.

 Carb Cleaner Spray and Nail Varnish Remover/Acetone are a couple of solvents to try....wedging the ball up and leaving it to soak in a  small container overnight, for example. Then a good poke around inside to pull out any solids.

  But if, as GB says, everything is clean then this becomes more of a mystery of the universe, and  changing the pick up pipe an annoying prospect.

 Hope it is a bit clogged, if not, maybe worth trying thinner oil, but clutching at straws a bit here.

 Swarfy.


 Additional. This got me thinking and I have just checked a couple of pick up pipes, and in each case the ball hardly lifts off the seat before being stopped by something in the housing. It comes to rest just 3mm from the flat face of the ball housing, not leaving much space for oil to pass the ball.
 I have never had a valve apart, but Roy Bacon's diagram on page 93 in my copy of BSA Twin Restoration would indicate the ball can rise a fair distance. So either the book is wrong, or I have a problem looming.

 Anyone with a sump plate off to compare how these valves are set up? Anyone successfully running without the ball?

[beezermacc]

"Additional. This got me thinking and I have just checked a couple of pick up pipes, and in each case the ball hardly lifts off the seat before being stopped by something in the housing. It comes to rest just 3mm from the flat face of the ball housing, not leaving much space for oil to pass the ball.
 I have never had a valve apart, but Roy Bacon's diagram on page 93 in my copy of BSA Twin Restoration would indicate the ball can rise a fair distance. So either the book is wrong, or I have a problem looming.

 Anyone with a sump plate off to compare how these valves are set up? Anyone successfully running without the ball?"


I had to replace the end of the suction pipe on a bike I built recently. (Some P.O. clown had sawn the tip off and removed the ball!)  On close inspection the pipe should have a wire across the inside of it which prevents the ball closing the pipe. It's difficult to see this from the outside but if you cut the enlarged piece of the pipe, which holds the ball, off you can see the metal bar from the other side. It is shaped so that the ball is held to one side. The bar is quite flimsy so, if it got damaged or fell out the ball would block the pipe. Similarly, if somebody hit the ball upwards, maybe with a punch or rod, thinking this was good thing to do to free it off (!!!!) the wire bar would break and the ball would contact the narrower pipe at the top and probably block it off. Not sure if this is helpful. Picture attached.

[Swarfcut]

Andrew    Thanks for shining the light.
    I (and probably most of the rest of us) have never really considered that the valve was anything more just a ball in a hole.  This could be the answer to many instances of scavenge failure.

 How BSA actually made it and ensured the bar/ wire stayed in place during brazing is a fine piece of production engineering. Roy Bacon's diagram looks to be an over simplification, but the wire is an ingenious way to move the ball to one side to clear the path for oil flow.

 In the now clearer scheme of things, looks like Steve's first step is to see how far the ball moves. To the top of the housing, bar/wire missing, not good, possibly blocking the pipe. Jammed down, no scavenge.   Moving as intended.....goodness Knows!

 Swarfy.

 

[JulianS]

Photo shows where the bar goes through.

[Swarfcut]

Julian.. Thanks, as always you make it so simple. I made it very complicated.  I assume that in production the bar was added last. Looked at Roy Bacon again and it makes sense.  The ball by my estimation should move a fair amount,  so looks as if my pipes require attention.

 Swarfy.