bigger tank for 80 sg

[markdam]

i have an 1980 xs special i stole. it is MINT 1 owner garaged ect anyway want to do a larger tank upgrade which is a better/easier upgrade? the maxim tank or the standard tank?

[Dennyz]

standard tank

[markdam]

why?

please explain why thanks and any others with input please jump in!

[John]

I have tried fitting an XJ11 tank to my bike, but it would have taken some modifacation to the rear of the tank,(shortening it)where it bolts to the frame and the seat would not latch in to place behind the tank. I have tried a larger 79XS750SF tank also, but there were no 'cutouts' on the bottom seam for the valve covers, and the front mounting pockets were in the wrong place. A good welding shop could probably relocate the pockets for you, but I didn't want to mess up a good tank from my 750. I have a spare Special tank that I want to try to enlarge some way. I too am tired of such limited range. About 90 miles is all I get to a tankful. I don't care for the bulkiness of the Standard tank, so I am very limited to what few options I do have.
I am thinking of cutting the spare tank lenghtways, stopping at the rear seam and raising the front by a couple of inches. I am not concerned by handlebar clearence because I have some risers that relocate my bars one inch up, and one inch back. It's still just a pipe dream, but maybe this winter I'll get around to it.

[TopCatGr58]

Hey there Mark,

I have a spare XJ tank that I'm going to put on my 81 Special this winter. Aside from the different mounting at the rear of the tank, I've also heard that the mounting wells/slots where the rubber cushions slide/fit into the underside of the tank are further back on the tank, making the XJ tank sit farther forward, causing it to possibly hit the triple tree on full swing turns!?

Fortunately I now have a welding machine, and so I think I can MOVE those mountings on the frame further back to clear the triple tree, but then again, I don't turn mine that far, except for making very tight parking at walking speed turns. I might just put some metal stops/bumpers on the frame to stop the triple tree from turning that far and leave the tank mounts alone!?

Moving the front mounts back might also move the rear mount further back, further aggravating the seat mount!?

I'll be taking pictures and possibly making a tech tip on how to do this, but it won't be too soon! I just prefer the teardrop look of the Xj tank vs. the Standard!

[Dennyz]

The standard tank will set right on a Special. The fuel lines will be different (no octopus) and the seat will be snug, but it will work. In that area, the frames are nearly identical.

Here is a project I started a while back and have not gotten back to.


6 Gallon Special tank

Just think, the range of a Standard and the looks of a Special.

[John]

Wow

That is exactly what I want to do with mine. Have you filled it to measure the capacity, or is six gals a close estimate? Also there is a big difference in the size and mounting of the petcocks from one style to the other. They will not interchange.

[Dennyz]

I filled it with 6.2 gallons of sand.

[markdam]

niCE!!!!!!!

well denny like tkat did with the forkbrace you may have a little side business there!!!!!!!! put me down for the tank mod!

[Dennyz]

Once I get the templates figured out, repeating the process should be fairly simple.

[Pain]

I have actuallyt pickup up a standard tank from ebay, 5.4 gallons, for not much ataall. They are listed often, and if you shaop a bit you can often find one iwht all the bits for less than 50 bucks.

I don' have a pic, but re-sealing, cleaning and painting is my winter project, when I finally decide it is too cold to ride (Which is not yet )

-Pain

[John]

Big tank

Denny, would you mind describing where you made the cuts on the tank to achieve a two gallon increase? I have studied the pic, but can't really tell where you cut it and just how large the inserts are. Like I said earlier, that is exactly what I want to do to my spare tank.

[Dennyz]

John,

I first cut the tank down each side where the tank transition from top to side. I removed the top by continuing to cut both ends at the seam. I then made a cut along the bottom of the sides where they transition to the bottom (the bend, not the seam). I wanted the tank to remain the same width at the saddle area, so I made a cut along the front of each side right at the seam.

At this point, I had the bottom of the tank and two sides flopping loose, attached only at the saddle area. This is a good time to clean the inside of the tank (sand blasting works great).

I welded a 1” strip to the front of each side (look close and you can see it in the picture) and a 1” strip to the saddle end of the top piece. I reattached each side to the front seam, bowing the sides out to get 1” extension to line up with the seam. I reattached the top by welding the front to the seam and bowing the top until the 1” extension lined up with the back seam.. By bowing the top, it puts the gas cap right at the highest point of the tank and adds a significant amount of volume

I then added filler panels to the resulting open areas, as shown in the picture. These areas exist on top of each side and on the bottom (I have not completed this step yet.). The petcocks remain in their stock location. This would be a good opportunity to eliminate the Special petcock mounts and install mount farther out for the Standard petcocks. I decided that would be another project, should this all work out. I duct taped all the seams and filled it with sand to make sure I had the desired volume. Less than 6 gallons is not worth the effort.

When I set it on my “SF” it looks pretty cool. It comes out to just over the valve covers on each side, yet is narrow at the saddle. The top rise is noticeable, but not objectionable. It has the bulbous look of a Standard tank, but much smoother lines.

As encouraging as the picture looks, I have a long way to go before I have a fuel tight smooth looking tank.

I used a bead roller on the edges of each filler panel to create an overlapping joint. The welding is being done with a MIG welder. A TIG would be a better choice, if I had one. The cutting was done with a air grinder with a cut-off wheel. The filler panel are cut from 16ga. steel (old car hood).

It is a long slow process with a lot of backing up. If the tank does not look good or hold fuel when done, it will be a waste of time. This being my first tank modification, I am learning as I go.

[UncleSpot]

SIX GALLONS ON A SPECIAL! YEAH!!!

Dennyz, if you ever get this worked out let me know... I love taking rides that are 125-200 miles from any gas stations - and that puts my '80SG "out of range"...
6 gallons would be GREAT! I also use my XS11 for my commuter 7 days a week and with 6 gallons it would only have to filled up once a week rather than 3 times every 2 weeks - it sounds trivial but would be worth it.
XSive regards,
RonATunclespot.com

[Ken Talbot]

Of course, you can get 6.3 US gallon capacity with an '81 Standard tank, but you loose the styling and fit at the seat of the Special. Denny's working towards the best of both worlds....