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A: Oil Pipework Series D oil tank leak


Gary Gittleson

Well Known and Active Website User
VOC Member
I've been struggling for some time with a persistent leak at the bottom of the oil tank on my D Rapide. One problem was that at some point in its life, an incorrect bolt was used in the lower rear mount. The threads must have been too long and it pushed into the tank under the thick welded-on washer. I fixed that by TIG welding all the way around the washer. The factory had originally just tacked it on in two or three places with the washer standing clear of the tank. That left a little well inside the washer where oil could still leak but would have to get past the threads of the mounting bolt. To solve that, I used some teflon tape on the threads.

That seems to have worked quite well but there has also been a leak from the banjo oil-feed fitting. The mounting bolt is now perfectly dry but the banjo is still leaking. It's not a lot, but after standing a couple of days, it's always wet and with more time, it drips on other nearby parts. I've tried various measures to cure it; a new banjo, stoning the mating surface on the tank with a very fine flat stone, new washers, tightening to the maximum that seems reasonable, sealant etc. I tried both fiber and copper washers. One problem has been in finding a suitable type of washer. The size is rather odd. The banjo diameter is about 16.7 mm, which doesn't work out to a normal imperial measurement. I am about to order some 17 mm ID copper crush washers to see if they might work. If not, I must admit I'm at a loss here. Any ideas?

Gary
 

Robert Watson

Well Known and Active Website User
VOC Member
Are the threads square to the mating surface? I have had a set of crank cases where the drain plug hole face was waaaaay off square from the threads. I made a 1/4 bsp pilot and then went onto that with a carbide spot face tool in a hand drill and probably took 1/16 inch from one side to square it up. Voila! Leak gone.
 

Normski

Well Known and Active Website User
VOC Member
The thread measuring 16.7mm will be 3/8 bsp, imperial pipe threads don't conform to direct measurement For washers look for 3/8bsp or NPT but if you were to replace the banjo bolt stay with bsp or you may get the wrong thread pitch.
 

Gary Gittleson

Well Known and Active Website User
VOC Member
I've tried Dowty seals but they don't work because there isn't enough mating surface.

The banjo bolt replacement was from the club and it goes straight in, so I'm sure the threads are correct.

By eye, the threads seem to be square to the face but I'll try to get a better measurement of that. I did order the crush washers. If it's square, my next try will be to use the new washers and some sort of loctite sealant. I have their special thread-leak sealant. I don't plan to use it on the threads but rather on the washers.

If it's not square, I'll have to figure out a way to fix that as per Mr. Watson's suggestion. But I'm quite sure it's not out anywhere near 1/16". With the banjo bolt in place, I can't see daylight between it and the facing tank protrusion. Since this is just an oil tank and not an engine casing, I can simply hold it up to the light and see it from all sides.

The bike's resting for the winter, so I'll take my time and post results as I progress.

Thanks for the replies.
Happy New Year!

Gary
 

tatty500

Well Known and Active Website User
Non-VOC Member
Gary,
I am speaking from a position of no knowledge at all of the D tank, but if similar practices to the B/C tank was used, there is a fitting like a cigar tube in the tank outlet to protect the filter on the banjo from direct access by bits. Cross drillings in this tube allow oil to the filter and thus to the outlet.


On a B/C this is all made up of three concentric, brazed together parts.

There is a large diameter boss in the tank.
Brazed in this is the holey cigar tube.
Brazed in the tube is the threaded insert that takes the outlet fitting.

The fibre washer for the fitting does not cover all these brazed joints so, if any one is imperfect slight weepage can occur in the area.

If all this is nonsense to a D owner..........sorry for wasting your time
Regards
Tatty
 

Cyborg

Well Known and Active Website User
VOC Member
Is the banjo bolt going in far enough to crush the washers? Are you sure it isn’t escaping between the banjo bolt bung and the tank? Maybe that’s a dumb question as I’ve never seen a D tank in real life. A bit of air pressure and some Sherlock leak detector fluid might help to confirm exactly where it’s escaping...or just seal off the banjo with a bit of hose and add some solvent to the tank. Fluorescent dye? Aircraft Spruce also sell a crankcase vacuum kit in case you want to reduce engine leaks as well.



 

Cyborg

Well Known and Active Website User
VOC Member
Gary,
I am speaking from a position of no knowledge at all of the D tank, but if similar practices to the B/C tank was used, there is a fitting like a cigar tube in the tank outlet to protect the filter on the banjo from direct access by bits. Cross drillings in this tube allow oil to the filter and thus to the outlet.


On a B/C this is all made up of three concentric, brazed together parts.

There is a large diameter boss in the tank.
Brazed in this is the holey cigar tube.
Brazed in the tube is the threaded insert that takes the outlet fitting.

The fibre washer for the fitting does not cover all these brazed joints so, if any one is imperfect slight weepage can occur in the area.

If all this is nonsense to a D owner..........sorry for wasting your time
Regards
Tatty
Well great minds think alike? Or we’re both talking nonsense.

My holey cigar tube came adrift.

F6C1CFB1-C3C8-4BBA-8404-D259F919A03D.jpeg
 
Last edited:

oexing

Well Known and Active Website User
VOC Member
You could do your own tailor-made Dowty washer, two piece type: A parted off ring from ss tubing plus an o-ring inside , half a millimeter more in height so you´d have half a mm squeeze on the o-ring for not so smooth faces. That way you can fabricate sizes to your likings.

Vic
 

brian gains

Well Known and Active Website User
VOC Member
if all mating surfaces are true a method I've used with success on rocker feeds as told by my Triumph guru and he says it was used in production. is to use Loctite on the faces of the annealed copper washer.
 

Gary Gittleson

Well Known and Active Website User
VOC Member
I think I've found my problem. The "bolt" has a reduced diameter (waisted) in the position of the contact with the tank. This allows the upper washer to move around as one tightens it up. My solution was to create a land for the washer with solder. I think the pictures explain it better.

The first picture shows the reduced diameter. The second shows what that allows the washer to do. The remaining two show what I did and how it seems to help.

It's not pretty and certainly not concours, about which I don't give a ... er .... hoot.

I did put some Loctite 567 on each side of both washers and re-assembled. Both washers are nicely centered. I'll be filling the tank with oil tomorrow and report in a week or so as to the results. If it's like before, it will show signs of leaking without running the bike.

Gary
 

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