Oil pump fibre washer

[Catz]

As the title says, how important is the fibre washer instead of a metal washer? Doesn't a metal washer retain it's shape over a distorted fibre washer?
Long story short, last week i picked up a basket case A10 for a bargain price i thought and the seller gave me some Classic Bike mags with some A10 related articles and in one from August 2010 was an article called how to fettle BSA twins by a bloke called Roger Sharman from Cake Street Classics in Suffolk. Below is a picture of part of the article relating to the oil pump.

EDIT: Well i've fitted a fibre washer under the end stud but still think it's a dumb idea. 

[Greybeard]

My instinctive answer is that a fibre washer will compress to fill the gap. The thickness of a steel washer may not accurately provide space so the pump could be distorted.

[Catz]

I can see that. 

[Ted_Flash]

"Fibre Washers" have varying thicknesses.  I could envisage the body being bent if an over thick washer was used.  From memory the correct one is thin, little more than the thickness of the gasket.

[JulianS]

An SRM one piece gasket avoids problems with fibre washer thickness.

[muskrat]

G'day Catz
It is most important to use a "washer" the same thickness (and material) as the gasket. The SRM ones are perfect. I make my own gaskets the same, don't use any goo and re-tension the nuts (or bolts) at the first oil change.
Cheers

[Colsbeeza]

Hi Catz,
Last time I fitted the original oil pump, I tightened it down lightly without the gaskets and ran a feeler gauge around the pump face to see if all was flat. It wasn't, so emeried the flat surface on a sheet of glass, and had to use a tiny bit of epoxy on the oil pump crank face where there was a groove. You must examine the face closely. The sticky-out bit at the end of the pump had corroded a few thou, so had to use a washer (cut from gasket paper) PLUS the full-face gasket mentioned my Muskrat and Julian. Quite a bit of fiddling to get it right, but worth it to have see good oil pressure (I have fitted a gauge). I have since fitted an SRM oil pump which does not need the "washer". The SRM gasket also has proper sized holes, but some aftermarket gaskets have holes either too small or not properly aligned. Some owners have had oil starvation problems due to the small hole sizes in the gasket. If you have the original studs with cycle thread nuts, use a tension wrench. About 10 ft-lbs is right.
All the best.
Col

[Swarfcut]

  Like Col says, always a good idea to check any pump for the pump body and the nose to be in the same plane. Any difference will distort the pump as it is tightened down and in extreme cases lock it up. Getting this right is simple, but well worth the effort. The use of the single round fibre washer is to match the thickness of the gasket between the pump body and the crankcase, but gaskets and washers do differ in thickness, the SRM one piece gasket is a better way to do it, at least the thickness of the material is the same beneath the three mounting points.

 More adventurous marquetry types amongst you could try a homespun one piece aluminium shim gasket, at least you could match the holes with some certainty, unlike some extremely **** poor commercially sourced examples. To recap...the pump needs to be tightened down without twisting, hence the material under the three mounting points needs to be of the same initial thickness and compressed to the same degree.

 Swarfy

 * Original expletive deleted by Forum software.

[Catz]

Thanks for all the replies lads, much appreciated.
I used a fibre washer exactly the same as in the photo below, it's 1/32" thick, which came from a selection of spares that came with one of the bikes. I re-used the main gasket.
It's staying put for now.

[muskrat]

G'day Catz.
The problem is the fiber washer will not compress as much as the gasket and WILL twist the pump. This little piece of mazark is the heart of the motor pumping it's "blood" around. If it doesn't work the motor WILL end up in a thousand pieces.
Cheers

[RDfella]

The problem is the fiber washer will not compress as much as the gasket

Strange - I've always thought the opposite. Reason: the area under the nose is quite small, compressed by one stud. The area under the body is compressed by two studs - but is a considerably larger area / stud than the nose. Therefore (IMO) the nose will crush its gasket more.

[muskrat]

G'day RD.
I see your point but the fiber washer is a different material. The "thumb nail" test shows it's a lot harder.
Cheers

[Colsbeeza]

Catz,
It looks like you have the gasket with the tiny holes.
Given what Musky and RD said, will you leave it as is?
Col

[Catz]

Mate i'm confused. It's like one persons idea conflicts with another.
I re-used the large gasket that was on the bike when i bought it, the bike was a runner and the only things i've changed in this engine rebuild is head gasket, head bolts, lock washers, the timing side bush, and the fibre washer. I changed the fibre washer because the one i took out disintegrated when put back together.
Honestly i don't know what to believe, if someone has a definite answer then please fire away. The SRM gasket looks like a goer.
At the moment Col i'm leaving it alone but like all things change is only a step away.
And so to bed...

[muskrat]

G'day Catz.
The definite answer is the SRM gasket!
Cheers