Banjo washers

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Jun 2026
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I have a leak from the rocker feed at the crankcase Banjo bolt. What is the best type of washers to use here? Aluminium, copper or fibre seem to be the main options but I was wondering if dowty washers would be more suitable? Also what size would they need to be? Engine is 1969 750cc.
 
Hello,
I've just aquired à 72 commando and my rocker feeds are leaking frome the cylinder head. Amazing how this thread arrives at the right time :)
Are Dowty washers also usable for the cylinder head banjos ?
Thank you all for your solutions !
 
Yes, I buy an assorted pack off Amazon in metric sizes and use them on rockets. Oil tank banjo, large sump, small sump even carbs.
 
Yes, I buy an assorted pack off Amazon in metric sizes and use them on rockets. Oil tank banjo, large sump, small sump even carbs.
Thanks, something like that ?
 
The AN supplied washer is Aluminium. It's what I use, I am not plagued with leaks, unless I am clumsy fitting them, or I am using a temporary oil pressure gauge fitting, but I do inspect/replace them when the oil feed pipes are disturbed, not quite single use, but maybe 2 or 3.

The washer on the Inlet tappet cover is also aluminium and also seems to work fine on the same basis of inspect/replace at tappet checks.
 
The AN supplied washer is Aluminium. It's what I use, I am not plagued with leaks, unless I am clumsy fitting them, or I am using a temporary oil pressure gauge fitting, but I do inspect/replace them when the oil feed pipes are disturbed, not quite single use, but maybe 2 or 3.

The washer on the Inlet tappet cover is also aluminium and also seems to work fine on the same basis of inspect/replace at tappet checks.
Do you anneal them?
 
Word of caution. It says these are good up to 120C. My under spark plug temp sensors have recorded up to 220C. It is a race bike, you may not reach these temperatures, in fact last time out neither did mine (mostly around 180 to 190C). I put this down to changing from Iron to Alloy barrels.

Obviously the location of the oil feed banjos is not as close to the combustion as the plugs, but probably well over 150C (guess). I will check with a spot thermometer at the weekend.

I use Dowty washers on oil tank fittings and fuel taps. They are great at what they do, but heat surely can be an issue.
 
Word of caution. It says these are good up to 120C. My under spark plug temp sensors have recorded up to 220C. It is a race bike, you may not reach these temperatures, in fact last time out neither did mine (mostly around 180 to 190C). I put this down to changing from Iron to Alloy barrels.

Obviously the location of the oil feed banjos is not as close to the combustion as the plugs, but probably well over 150C (guess). I will check with a spot thermometer at the weekend.

I use Dowty washers on oil tank fittings and fuel taps. They are great at what they do, but heat surely can be an issue.
Interesting to see the difference in temps between running iron and alloy barrels Steve 👍
 
Word of caution. It says these are good up to 120C. My under spark plug temp sensors have recorded up to 220C. It is a race bike, you may not reach these temperatures, in fact last time out neither did mine (mostly around 180 to 190C). I put this down to changing from Iron to Alloy barrels.

Obviously the location of the oil feed banjos is not as close to the combustion as the plugs, but probably well over 150C (guess). I will check with a spot thermometer at the weekend.

I use Dowty washers on oil tank fittings and fuel taps. They are great at what they do, but heat surely can be an issue.
Yes I thought about the heat issue too, in a first time, I will try to tighten the banjos with a torque wrench to be sure the setting is correct.
 
I have always used permatex white thread sealant on weeping banjo washers of all types. But once tightened and set, if you take it apart or want to tighten more, it must be dissembled and the hardened white residue cleaned off.
John, Flange sealant is a great idea. Why didn't I think of using it before.
Easier to clean off.
Dennis
 
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