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Sump Oil Filter Cover

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I'm currently undertaking Norton's version of The Labours of Hercules, ie I'm trying valiantly to eradicate the many and varied oil seepages that plague the bike. With regard to the oil filter cover, the one fitted to mine is 'dished' rather than being flat (it's the edges of the cover that I'm referring to, that sit up against the part of the crankcase surrounding the filter orifice). Now this puzzles me insofar as the crankcase itself appears to have a flat surface surrounding the hole so why would the cover that bolts up against it not be flat too? Or is it just an idiosyncracy on my bike? I've looked at the exploded diagram in the parts book for a clue and, as far as can be ascertained from that, the cover does appear to have a flat seating 'lip'. Thought I'd best check here before taking a large hammer to the cover and beating it flat. Anyone know the answer?

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Hi Howard, your pressed steel sump plate sounds correct - the problem I found was they become distorted over the years and never seal satisfactorily.  Frankly I became so frustrated by mine that I bit the bullet and replaced it with the excellent aluminium, finned one with the magnetic drain plug that the NOC shop sells for £42.50 + VAT - you will find it under the Lightweight Crankshaft, Con rods etc section along with new gauze filters.   They are expensive but I think money well spent.  Since I installed mine with a new gauze and gasket either side helped with a smear of silicone sealant it has remained completely oil tight and gives the huge advantage of being able to check the mag-plug from time to time to monitor engine health.    I have done three oil and filter changes in the last 18 months, replacing the filter and gaskets and it still remains leak free.   Hope that helps!

Nick 

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Thanks for that, Nick. Sounds like I shall probably have to do a bit of bullet munching too if I'm to achieve an oil-tight sump cover. Is the super-duper NOC version flat-faced or is it also dished?

Howard

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The gasket faces are quite wide, flat and without a lip but there is a dished, pear shaped area around the mag plug which the oil collects in after passing through the gauze filter to provide a pool for the return side to scavenge from.

Nick 

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From the description you give of the replacement cover it does seem to suggest that the originals should be flat on their mounting areas too as they do, of course, have a bowl-like depression moulded into them, presumably to allow room for the filtered oil to collect, prior to finding its way back into the oil-return system. I'm still rather puzzled though as to what could cause the plate to become bowed, side-to-side and also back-to-front as it's always held, tightly-clamped, against the flat underside of the crankcase filter mount. I must admit that it does actually look as if it was made in that shape which, if so, leaves me completely nonplussed.

Sump filter and plate.

Hi Howard

       The images below show how the sump plate, sump filter and paper gasket (2no) are supposed to  work. The lead gauze filter was originally thicker than the folded perimeter upstanding rim on the sump plate . After nearly sixty years the lead squashes down and so has to be compensated with extra paper filters to suit. If this is not done the sump plate distorts because the perimeter rim of the sump plate touches the crankcase when it is tightened.

 

GRAHAM

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Many thanks Graham for your very helpful clarification. Your explanation also tells me why my bike sports five (count 'em, five!) gaskets down there rather than the regulation two shown in the Parts List illustration. What a weird engineering arrangement! I can understand the function of the (two) gaskets pressed up against either side of the filter lead surround to keep the oil where it's supposed to be, and also the folded-over lip on the cover to allow space for the lead seating plus gaskets but why, in all that's holy, would you make the lipped surround in a curved form rather than flat? What was that supposed to achieve? The fact that the updated version described above by Nick has a flat seating suggests that something is/was wrong somewhere. 

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A final thought Howard, it may seem extravagant but I now always replace the gauze filter with it's lead surround at each oil change for exactly that reason!   Back in the day as a youth I couldn't afford such extravagance and I remember the lead became thinner and thinner and the plate more distorted every time it was tightened down so it always leaked despite the use of copious amounts of Red Hermatite and home made paper gaskets - I hang my head in shame at the thought!!!

Nick    

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It certainly makes sense Nick and I shall, in all probability, treat the old nail to a new filter, gaskets and 21st century filter cover. However, and as a last throw of the 'make do with what you've got' dice, I've cleaned everything up, slathered the lot in Three Bond and stuck it all back together with fingers crossed. One nagging thought though with regard to the copious amounts of goo I've applied, what will happen if the goo gets squeezed over the oil-return hole in the lead surround? Presumably the oil will still find its way back to the oil tank by short-circuiting the sump filter itself, so (I hope!!) we're not looking at an engine-seizure scenario are we?

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I have agonised over that in the past having done the same thing in my youth - particularly as the only return route for the oil is via that oil way in the sump!    A simple check is to start the engine and check to see if there is a healthy flow of oil from the oil return pipe in the oil tank.   Good luck! Nick  

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Nick, I assume, from your lack of confirmation to the contrary, that you 'got away with it' then, from which it's probably reasonable to infer that yer 'ole wasn't actually blocked, despite your concerns. Now, the question is 'do I feel lucky, punk'. Mmm, I wonder. Presumably, if the return hole is indeed bunged up, the first indication I would get would be when the oil in the sump is forced out of the engine breather, rather than being able to get back to the oil tank. Other than a right royal mess on and around the bike I'm assuming (that word again!) no damage would occur, as the moving parts would still be receiving a supply of lubrication, albeit on a total-loss basis. Sound right to you?

Howard.

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I started the engine, checked the oil return was flowing normally and got away with it as a youth Howard but spares were plentiful and cheap back then!    My advice is bight the bullet, buy a new filter, gaskets and aluminium sump plate and enjoy a leak free bike and peace of mind over oil circulation!   Nick  

 


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