73 850 oil tank?

Anyone have an idea where I could get a new repop or old and reconditioned oil tank for a 73 Commando? Mine just fractured the rear mount in the traditional fashion but we’ve just hit the prime of our short riding season and I’d like to ride this bike, not work on it. Thanks!!

Take it off and fix it up no need to replace a quick braze or weld and rubber mount or not use the mount at all will stop it from doing it again, common problem with Commando oil tanks.
Fixing it will be quicker than ordering and waiting for a new replacement and always someone who has a welder.

ashman said:

Take it off and fix it up no need to replace a quick braze or weld and rubber mount or not use the mount at all will stop it from doing it again, common problem with Commando oil tanks.
Fixing it will be quicker than ordering and waiting for a new replacement and always someone who has a welder.

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I don’t think you will have any problem with repairing your tank.Just find a good welder and get back on the road!

As mentioned above, a quick & easy repair. Find a talented welder.

linker48x said:

Anyone have an idea where I could get a new repop or old and reconditioned oil tank for a 73 Commando? Mine just fractured the rear mount in the traditional fashion but we’ve just hit the prime of our short riding season and I’d like to ride this bike, not work on it. Thanks!!

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Andover stocks new ones. With the exchange rate, credit card fees, and shipping it's around $500. If you can braze (preferred) or weld, you can fix it in around two hours (getting it off, cleaning, brazing, painting, putting back together).

Welding is better than brazing, once brazed the steel is contaminated and can never be successfully welded. I fit stiffer rubber buffers with larger studs. On the bottom I grind off the threaded insert, weld a plate over the top in case there is a hidden crack and then after painting rest the tank on a rubber buffer glued to the bottom. The tank is then only held at 2 points putting less strain on these 2 points as long as you size the rubber buffer correctly.

linker48x said:

Anyone have an idea where I could get a new repop or old and reconditioned oil tank for a 73 Commando? Mine just fractured the rear mount in the traditional fashion but we’ve just hit the prime of our short riding season and I’d like to ride this bike, not work on it. Thanks!!

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Understood about the short riding season.
A repair can be made quickly.

kommando said:

Welding is better than brazing, once brazed the steel is contaminated and can never be successfully welded.

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No doubt that welding after brazing is hard to impossible depending on the type of welding.

Oil tanks repaired by weld often break again - not in the weld but outside of it. Not an expert in welding, brazing, or metallurgy, but I assume that's because the thin metal become brittle in the process. Also, it is very difficult to weld at the top where the bracket is close to the tank and get it sealed.

Tanks I've welded have often needed to be repaired again. I've never had a braze fix on an oil tank fail. I do flow the braze over the area not just in the crack and sealing the top is simple and strengthening.

I assume brazing changes the steel less because the steel is heated to a much lower temperature and over a wider area.

kommando said:

On the bottom I grind off the threaded insert, weld a plate over the top in case there is a hidden crack and then after painting rest the tank on a rubber buffer glued to the bottom. The tank is then only held at 2 points putting less strain on these 2 points as long as you size the rubber buffer correctly.

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When cNw does their process to the tank they do as you say at the bottom, and they double up the rear mount. It works fine as long as you don't have the MK2A type of battery box - nothing but the battery to keep the oil tank from moving inward at the bottom. For others, the tank rests on the rubber at the bottom, the front and rear top mounts remain each with a rubber isolation mount, a rubber pad goes between the tank and battery box, and the oil tank cover keeps the tank bottom from moving outward. Therefore, it is isolation mounted all around.

Good thread thank you. Greg confirms my approach (esp the rubber between tank and battery box) on Mk2 is good.

Would CNW have an oil tank ready for quick shipping?

Jdub said:

Good thread thank you. Greg confirms my approach (esp the rubber between tank and battery box) on Mk2 is good.

Would CNW have an oil tank ready for quick shipping?

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No, they stopped that long ago. You send your tank and it goes into the batch they have on the first of the month. It is returned near the end of the batch's month.

It's a great service for the off-season or when building a bike. It comes back spotless inside and powder coated. For all they do to the tank, the price a very reasonable.

For a really quick fix of your tank, clean the area up, seal it, put a thin rubber pad between the tank and battery box and inside the battery cover, and don't use the top rear mount at all. You can probably seal it with RTV. You could use JB Weld but it might be hard to get off for a later fix. Then you can send to cNw in the off-season. See: https://coloradonortonworks.net/cnw-specialized-modifications

I have done a few brazing jobs on oil tanks and as Greg said not only braze the crack but around the crack area as well get the right heat and let the braze flow, plumbers are good at brazing lol.

My tank had the same mount tang break, no cracks into tank, no leak. I've just packed foam rubber at the rear top corner to support, a rubber pad at bottom where bolt previously was, and used a couple of zip ties around frame spine and filler neck. Completely stable, no more strain on remaining front tang. Been great for 10k miles like this. No urgency to get a weld job.

Thanks guys, I found one and will clean it out and put it on. I'll fix mine this winter, I sold my torches and I only have a short riding season, so this is best for me. For the moment my own tank with the broken tab is zip tied on to stabilize it.