Oil tank leak

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Excalibur
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Oil tank leak

#1

Post by Excalibur »

My oil tank has a small leak at the lower bracket. Enough to be annoying..
drp.jpg
Drips off left bracket onto ratchet top. Other bracket where battery box attaches, it drips off the lower end of that.

Leak is very slow but will only get worse. I plan to pressure test with 5 -10psi to identify crack/s.

History: When bike came to me, it was missing the mount under the battery box. I believe this added extra stress to the oil tank. Actually even with all rubber mounts renewed, It's apparent there is flex movement going on just from vibration.

Studying the topic, there's a lot said about this repair prospect. Some say braze, TIG etc. Fully weld bracket right around mentioned a few times. Didn't think much of Tank Sealer idea, nor of JB weld. New tanks are available but reviews are mixed, upwards of 2hundy to land one, more if via Ebay.

I was given an oil tank a few weeks ago but it's not the same pattern exactly. It has a separate filter, is already brazed on the lower mount and is leaking again. Am envious of the side filler/dipstick. Wondering if I can stitch that onto my tank as I write..

Is there any strengthening method known to work well? Anything to spread the load and reduce flex. Looks like a stress area right beside bracket to battery.

For the moment bike needs to stay together for Brake Declaration cert, then all the other steps it needs for the registration license. After all that I can slide the tank out and give it some doctoring. Son is really good with TIG.

Thanks for any tips, points, ideas..
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RooDog
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Re: Oil tank leak

#2

Post by RooDog »

Brazing is NFG. Once brass is applied the metal is "poisoned" and no longer able to be welded. It also has a tendency to crack as the braze cools, so best to avoid that process. Period.....
Even JB, or any similar epoxy is better than brazing, as that stuff can be removed for a later weld repair.
TIG would be best.

PS: I hate the OE cracker box oil tanks with the battery hanging off the side, ( it's like some MoCo engineers said "Hey fellas, we forgot to allow for a battery, let's just hang it here."), and have used a hard mounted AM wrap around, side fill, tank on my '68 FL for over 40 years with no issues.....
....RooDog....
Architect
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Re: Oil tank leak

#3

Post by Architect »

I had the same issue with a chrome tank on my 1970, I thought for 6 months the oil drain plug was leaking. Turns out the bracket at the weld was the culprit. 10 PSI was all I needed to find the leak. My tank was likely after market so I opted to find an OEM replacement. Found one with usable black paint, cleaned her all up and was quite proud of myself. Until I went around the block and the leak was still there!?!?!?

New/Old tank had a pin hole. At least it was OEM and the pinhole was in an easily welded location. Got her welded up and back on the bike, all was well again in my world.

Then we had a minor accident and have not ridden the bike since, still in pieces waiting on chrome.

My summation, very hard to fix the leak at the welded on bottom bracket, OEM tanks are plentiful on the Bay or Swaps. Just find one without a pinhole in the bottom. Good luck.
panheadrider1961
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Re: Oil tank leak

#4

Post by panheadrider1961 »

Shop Shovelhead oil tanks eBay you can pick up a good for around 60.00 no dipstick but trim
Excalibur
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Re: Oil tank leak

#5

Post by Excalibur »

Thanks for the great thoughts, awesome.

Roo, Agreed about brazing. Definitely won't be doing that. Like your description of tank as a Moco afterthought. Flexing a heavy battery off the side is an engineering fail. Got them through warranty I suppose.

Architect, nice story and typical of what we go through with these old things. If only it could talk, this bike would have quite a few tales to tell.
It's had more hits than the Beatles.!

Panheadrider61, USPS has be been suspended to NZ for maybe a year so far. No sign of it being lifted.

Plan
Thoroughly degrease tank. 10psi test. TIG crack. TIG some sort of bracing or gusset.
In the welding game we say that whenever a crack is welded it will often break in the same place. This can be because the metal is fatigued or the area is a point of stress. Typically we weld crack, then weld a fresh piece of steel, bridging over the crack. I have a few ideas on the boil. Will talk with son who's a TIG specialist. Then we'll agree to a plan and make it happen. Post back with updates as we go.
db13
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Re: Oil tank leak

#6

Post by db13 »

Have a 1978 anniversary sporty ....back in the 80's gas tank started to leak around the filler neck then the oil tank started to leak around a mount bracket...not wanting to destroy the paint on either I used jb weld and both are still going today leak free.Also have a 1981 FXWG where the battery burnt a hole in my oil tank and fixed it with jb weld also...still going.
panheadrider1961
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Re: Oil tank leak

#7

Post by panheadrider1961 »

Sorry you have no delivery service
If tig welding fill tank with ice as much as possible use silica bronze rod low temp melt and strong bond scale as much as possible around crack and wipe down good a few times with acetone to get clean as possible ice helps chill metal quick to help with weld heat sink to avoid spider cracking away from weld area good luck
Panacea
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Re: Oil tank leak

#8

Post by Panacea »

My wife said you could just throw it in the dish washer for a nice clean up :D
Excalibur
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Re: Oil tank leak

#9

Post by Excalibur »

Got the oil tank repair done with mods. It turned out, bottom mount plate had to be fully welded to tank skin. Leak was somewhere under the plate probably at a spot weld. Suspiciously it looked like the spot adjacent lower front mount. Custom bracing underneath and battery box upper mount fabricated by hand. Spent quite a bit of time ensuring stress at mounts was minimized, shims, alignment etc.
Tank skin is very thin. Welding by TIG. Braces/brackets 2mm & 3mm.
Oil tank and battery tray were not perfectly square to each other but anyway I made the mount to suit and shimmed it for fine adjustment.
Bike came to me with a missing battery box mount, the one under. Therefore the oil tank would have been taking quite a hiding with the weight of the (existing) big, heavy battery.

Early setting up for upper battery box mount bracket..
bbx3.jpg
How I did the filler bung. It needed to be in the front corner to clear seat. The tip is to bore the hole then make the insert exact size. This makes for easier TIG because there's no gap to bridge.
bbx4.jpg
Welded and ready to install
bbx1.jpg
Underneath, note hole for oil hose to pass through.
bbx2.jpg

Have run the bike but yet to road test. Let's see if it works. Hope this helps.
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FL54
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Re: Oil tank leak

#10

Post by FL54 »

Nice job.
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