Baffled, confused and covered in oil!!!!!!

[Triton Thrasher]

Strange stuff.  Looks like a gauze that would work OK.

[limeyrob]

Just looked at images of the original A10 set up. The gauze is a top hat shape soldered into the cover.  That means it has quite a bit more area with the sides as well as the top.  All the replacements are flat but as you have proved, its not the same.   If you fit a return filter you could probably do without the gauze. Mine has a replacement flat gauze so I will be watching this closely.

[bikerboy]

I can think of two possibilities: the wire pin in the pickup pipe is missing, meaning the anti-drain ball can go right up and block the pipe, or the sump gauze is too fine and oil can't drain through it fast enough to get to the return suction pipe.
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Going through this thread I just noticed this comment from RDfella

Seems like he was right and as the gauze was brand new I sort of glossed over it. Well done RD shame I obviously discounted the possibility.

[muskrat]

G'day BB.
Great to hear you found the culprit. 
Strange as I have those fitted to both my A's. The Cafe breather is plumbed back to the oil tank but the A7 is standard and never had that problem. I can't remember where I got mine from but could it be that different manufacturers use different gauze ? Mine do look like yours.
Cheers

[KiwiGF]

Just looked at images of the original A10 set up. The gauze is a top hat shape soldered into the cover.  That means it has quite a bit more area with the sides as well as the top.  All the replacements are flat but as you have proved, its not the same.   If you fit a return filter you could probably do without the gauze. Mine has a replacement flat gauze so I will be watching this closely.

I think this gauze is to protect the scavenge side of the pump from big particles? (rather than the bigger job of keeping the oil clean).

My bike has this gauze, I guess there are some finer than others 

[limeyrob]

I agree its to protect the pump from bits, but if the engine is creating bits like that you have bigger problems.  With a return filter everything should be getting taken out by that so it can't come round again and there's the pick up filter in the tank too.  I do think its worth having the sump gauze in for the first few runs after a rebuild, no matter how careful there always seems to be a lump of Hylomar that finds its way to the bottom.

[CheeserBeezer]

The ones I use and sell have 'SRM' embossed around the edge.

[CheeserBeezer]

It's great that you've got it fixed. Theoretically, if the sump plate is properly sealed against the bottom of the crankcase, the return suction pipe should cause a vacuum in the void where the oil usually collects, sufficient to draw the oil through the gauze. This leads me to wonder whether the sump was sealed properly and maybe the suction pipe was drawing air instead. Whatever!....It would appear to be something to do with the gauze plate.

[Jules]

wow, what an interesting issue and long drawnout solution!!
I have been looking to fit a sump plate with a magnetic drain plug for sometime, just never got around to it. However, I would like to do that and have been looking at a few different styles, is there a particular version that fits without any modifications and works best (I have noted some with flat gauzes ie minimum volume under the gauze and wondered if thats a good idea, maybe the suction tube can sit too close to the bottom flat face for example??
maybe useful thoughts to close out this thread..

[limeyrob]

I have tapped my steel sump plate 3/8 BSC and used the drain plug 82-5343 with a Dowty washer.  In the past I have made magnetic sump plugs by drilling and pressing in a neodymium magnet but I've only found them useful on gearboxes where they will catch a tooth chip and stop it doing more damage.  In the engine its mostly, if not all, non-ferrous.
I did spend quite a bit of time adjusting the pick up and gauze to get a good fit between the pipe and the hole but I'm not sure its possible to get any form of seal.

[Triton Thrasher]

I did spend quite a bit of time adjusting the pick up and gauze to get a good fit between the pipe and the hole but I'm not sure its possible to get any form of seal.

If the gauze is domed or raised, like the thing below, the oil level might never reach the hole, so a seal might not be important.

[limeyrob]

That is the original design and I think it is better.  My gauze was missing and I couldn't find a solder in replacement, only flat plates.  This discussion has got me thinking whether its possible to buy some flat gauze and make one.  I've been making patrol tap filters from brass gauze and its gone better than expected.
Someone has old stock correct sump plates and gauze on e-bay but they are £35!

[Swarfcut]

 Good to know yet another facet of this syndrome has been revealed. I'm considering the viscosity of stone cold oil and whether on start up the residual oil coating on small mesh is enough to cause the blockage.  But all through this saga I'm sure the oil return has been accepted as closer to expected normal than otherwise.

 As far as lubrication goes, early post indicates Straight 40.  Would anyone consider a modern synthetic low viscosity oil eg 5W30 as being suitable? I know thin oil is a recipe for wet sumping, but this stuff is used on car engines with more stress than our motors.

 Rob's picture shows support wires within the dome. These domes  come in various forms, I've seen one which is made from sheet, with small holes punched. Not one I would risk. The dome offers a greater surface area for filtration over the flat plate, which looks to be not such a good idea.

 Swarfy

[limeyrob]

I've done a web search and here are pictures of a new original part 41-620 and a quality flat replacement.  Its hard to be sure but I think the original part is a more open mesh.

[Jules]

my biggest concern with the flat plate is the lack of clearance between the pipe end and the plate....