Not all motorcycle oil tanks were created equal. If you are looking for an oil tank for your bobber, chopper or custom motorcycle you will want to read this brief article. In it, we will compare oil tanks from several different companies, discuss pros, cons and get into core things to look for when deciding which oil tank to purchase. Major inspection points are general construction and weld quality, mounting points, the weight of the oil tank, location and style of fittings and filler cap.
The two oil tanks in the middle are from Lowbrow Customs. The tank on the far left and far right are from other shops. At first glance they look quite similar. Read on to find out the differences!
Substandard mounting tabs and grade 2 hardware and only two mounting points doesn't leave us feeling confident in this oil tank.
Comparison And Review Of Chopper Oil Tanks
Watch the video about comparison and review details about Chopper Oil Tanks
Oil Tank With Thin And Short Mounting Tabs
The first thing I noticed about this oil tank were the mounting tabs. The tabs were included with the oil tank, however, they are so thin and short as to be completely useless. Hardware was also included, but is grade 2, the cheapest, least reliable, common grade bolts. There are two mounting bungs located on top of the oil tank, though a third mounting point is sorely lacking. If you actually ride your motorcycle you will want to ensure secure mounting. Nothing spoils a fun day out riding like breaking an oil tank mount.
The domed ends are spun steel and look nice. The welds, however, were ground, and the ends of the tank are not square at all. They are wavy, and if I were running this oil tank I would definitely pressure test it to make sure the grinding didn't open up any pinholes in the weld. If you want the tank to have a nice finish you would have to grind the ends square and then likely re-weld. This tank weighs in around 3.6 pounds, which is right around where it should be.
The oil feed (sends oil to engine), oil return (where hot oil returns to the oil tank from the engine) and vent bungs are all typical for aftermarket tanks. The feed is at the bottom, while the return and vent fittings are at the top. This all works well enough, the only downside is that you have to route your oil lines up over the back of your oil tank, which can be unsightly.
Lastly, the filler cap provided is a very sloppy fit in the threads. It also has only a few threads on it, which could cause you to easily lose it from vibration while out riding. While a simple problem, it is a real pain to seal your oil tank up to get you home and then have to order a replacement cap. There is an o-ring seal on this cap, but the o-ring literally falls off when you take the cap off. It is too large in diameter to stay on the cap and too narrow in thickness to offer any sealing between the cap and the filler bung.
Oil Tank With No Mounting
The only nice thing about this oil tank is the cap and the welds. The large disadvantage of this oil tank is that it weighs over 5.5 pounds.
This oil tank has no mounts whatsoever. It is up to the user to fabricate and weld mounts to the body of this oil tank, which is just a basic vessel with a filler bung and cap and three fittings for the feed, return, and vent lines. Same as the last oil tank, the oil return and vent bung are on top of the tank, which means you have to run the oil lines up to the top of your tank, while the oil feed line is located on the bottom of the tank. It works, but it doesn't allow for clean oil line routing. The filler cap on this tank is aluminum and is well machined with plenty of threads, a far cry from the substandard cap on the last oil tank we looked at.
The domed end caps on this oil tank appear to be fence post caps. Think of the yellow poles at gas stations so you don't hit the pumps; that is what these caps are made for. Something that doesn't come through in photos is the weight of the oil tank. This oil tank is VERY heavy compared to all the others and weighs in at more than 5.5 pounds.
A quart of oil weighs a hair over 2 pounds. Add three quarts of oil to this oil tank and there is almost 12 pounds hanging off of your frame. I mention this because you best be sure that you have quality welds and very beefy mounts (in three locations for sure) to ensure that this oil tank doesn't end up destroying itself from vibration.
This tank can be the basis for your custom motorcycle's oil tank, though it isn't as user friendly as other options that already have mounting bungs in place. Also, my opinion is that the unnecessary wall thickness and weight of this oil tank is a downside and can lead to failure if it is installed by someone without much fabrication experience.
Triumph Oil Tank
Dimpled Steel Motorcycle Oil Tank for Triumphs and British choppers is handmade specifically for motorcycles. Not one single 'off the shelf' component was used.
Full disclosure: The following two oil tanks are from Lowbrow Customs, so perhaps I am biased. However, I do believe that these are the highest quality chopper oil tanks available. First off, every single component used on these oil tanks is made for that exact purpose.
No 'off the shelf' components are used. We had tooling made for our domed and dimpled end caps and have them spun specifically for our oil tanks. The filler neck, cap, and all the threaded bungs are from Lowbrow Customs. They are proudly made in Cleveland, Ohio, USA.
This Triumph Oil Tank, like all Lowbrow Customs oil tanks, feature three mounting bungs, two top and one bottom. They accept standard 5/16"-18 hardware, and are blind-threaded (the threaded holes do not open into the body of the oil tank), tophat style bungs. They are TIG-welded into place, as is the 1-5/16"-12 tpi, vented filler cap and the Triumph OEM-style filler bung (that accepts a stock-style 82-3179 Triumph oil feed filter).
The return line on this oil tank goes to the special, brazed T-fitting. The small tube coming off of the return is for a 3/16" ID oil line needed on British motorcycles such as Triumph and BSA to oil the rocker boxes. This oil tank weighs in at a reasonable 3.5 pounds.
Harley-Davidson Big Twins Oil Tank
Lowbrow Customs Domed Steel Motorcycle Oil Tank for H-D Sportster Big Twin and Universal Choppers features internal plumbing for the cleanest oil line routing.
Similar to the Lowbrow oil tanks for Triumphs / British choppers, we also offer this option that is perfect for Harley-Davidson Big Twins and custom Sportsters, as well as any other make or model motorcycle. A machined, 1-5/16"-12 thread per inch filler cap is included and is a perfect fit, with an o-ring seal ensuring a leak-free tank. Three mounting points offer easy and reliable installation (using one of many possible mounting tabs) while the vent, oil feed and oil return bungs located at the bottom of the tank keep your oil line routing clean and easy.
This oil tank features internal plumbing for the vent and oil return lines, something not offered by other aftermarket oil tanks. The vent and oil return bungs are specially machined and feature furnace-brazed tubing to keep everything as tidy as possible. This tank weighs in at 3.5 pounds. It is completely TIG-welded and proudly made in Cleveland, Ohio, USA.
Hopefully you are now armed with more knowledge that will help you during your current and any future motorcycle builds.
How To Make A Custom British Motorcycle Oil Tank
This is just one of multiple ways you can plumb a custom oil tank. I used one of our DIY Oil Tank Kits and decided to do a vertical oil tank, with the return line coming in at the top of the tank. This saves time instead of cutting each piece and making the fittings and bungs, but you can easily do this with some assorted size steel or aluminum tubing and round stock. For an oil tank for a British motorcycle such as a Triumph or BSA, you need to route oil to the top end of the motor from the return line going back to the oil tank.
On a stock tank this is done with a 'T' fitting, and that is what we do here. The DIY Oil Tank Kit comes with the plumbing ready to go, or if you make it yourself you just want to use 5/16" ID tubing for the main return with a piece of 1/8" to 3/16"OD tubing for the smaller arm of the 'T', which is where you use oil line to run up to your rocker boxes.
Step 1: Decide The Type Of Oil Tank
The first step is to decide what type of oil tank you are going to build and where you will locate the filler neck, mounting bungs, return fitting, feed fitting and vent. Once you draw a rough blueprint or mark it on your tank you are ready to begin.
Step 2: Drill The Holes
Here I used a drill press and a 1-1/2" metal hole saw to cut the holes needed for the filler neck and the oil feed fitting, both of which were 1-1/2" OD. This would have been easier if I took the time to swap out the machinist's vise on my drill press to a larger one, but I was able to hold it in place while quickly drilling the holes. Use cutting fluid when doing this to extend the life of your drill bit and cut the steel easier.
Step 3: Prep The Metal For Welding
With the holes drilled, prep the metal for welding with a bit of sand paper to get any rust off and then wiped it down so it was clean and oil-free. Slide the filler neck inside the hole you drilled and tack it in place, do the same with the oil feed bung, then once you are sure they are straight go ahead and weld them all the way around, making sure you get good penetration and you don't leave any pinholes for oil to leak from.
For the oil tank vent, which equalizes pressure inside the tank while oil is returning, we are going to simply weld the vent fitting over the hole in the top, facing it backwards so a piece of oil line can be run towards the rear of the bike to vent.
If we were running the oil return from the bottom of the tank, you use this 'snorkel tube' so that the hot oil returns to the top of the tank, and the cooler oil at the bottom is sucked from the feed fitting. Since I am setting this up to return at the top of the tank I am going to cut the tube shorter and weld it to the fitting.
Step 4: Drill A Hole In The Body Of The Oil Tank
Then drill a hole in the body of the oil tank where you want the return fitting to be located. Just be sure that it will be high enough to return oil above the actual oil level of the tank. It is nice to locate it so when you look through the fill cap you can visually confirm that there is oil returning to your tank when the bike is running.
Step 5: Weld Oil Tank
Weld the top and bottom to the body of the oil tank before welding the return fitting, this way you can easily rotate the body of the tank and do the finish welding without having to worry about the return tube sticking out.
All that is left is to weld the mounting bungs in place. Here we used two mounting bungs that will match up to two steel bungs that go through the vertical seat post tube on the motorcycle frame, giving a very secure mounting location.
Now you have a finished oil tank. There are almost limitless possibilities as to what you can come up with, this was just one idea that took an afternoon to make a reality. You can read a complete guide how we mount an oil tank on the motorcycle with very detailed steps and images.