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XS750 tank on a XS650?

Discussion in 'The Garage' started by SDLars, Sep 12, 2018.

  1. SDLars

    SDLars XS650 Member

    Seems I read somewhere where someone had fitted a 750 tank on a 650 for extra fuel capacity. Anyone know what kind of fabricating had to be done to accomplish this? Other options for more capacity?
    Thanks in advance.
  2. MaxPete

    MaxPete New knee installed but still breakin’ her in.... Top Contributor XS650.com Supporter

    Basically, it will involve swapping the forward mount “pucks” from the XS650 tank to the XS650 frame because the sheet metal cups that receive those pucks are on the XS750 tank (i.e. the gender of the forward mount setup is reversed on the 750 tank) and it’s way easier to simply move the pucks than weld new mounts on the thin sheet metal tank. You will also need to do a little minor surgery on the rear tank mount

    NOTE - the pucks will mount in a slightly higher and perhaps more forward position than the present ones on the XS650 frame from what I can tell.

    If you use the Forum search engine, I’m sure you’ll find details. A member named Larksnostril did a beautiful job on his as did Brassneck.

  3. 650Skull

    650Skull Dogonit Top Contributor

    Here is a sloution without removing the cups from the XS650 frame

    a thread on the swap did remove the 650 cups. Some details on painting

    Another thread with some extra detail info....worth reading

    Interesting 73TX cafe build with an XS750 Chrome powder-coat tank.......
    gggGary likes this.
  4. fredintoon

    fredintoon Fred Hill, S'toon. Top Contributor

    Hi SDLars,
    like they said, an XS750 tank will fit but you have to work at it.
    Your profile photo shows a Special.
    An XS650 Standard tank is one gallon bigger and drops right on.
    IMG_0024.JPG IMG_0019.JPG
    Like this one on my Heritage Special.
    gggGary likes this.
  5. SDLars

    SDLars XS650 Member

    Great info guys. Thanks again.
    gggGary likes this.
  6. ThatXS650Guy

    ThatXS650Guy More Sparky than Speed Racer

    I've done it fairly recently. Let me know if you have any questions.
    Be advised your stock seat may not fit anymore since the 750 tank is a bit longer than the Special tank.

    Attached Files:

    Superjet, gggGary and nj1639 like this.
  7. MaxPete

    MaxPete New knee installed but still breakin’ her in.... Top Contributor XS650.com Supporter

    ThatXS650Guy: sure looks sharp!

    It looks like you're using the stock petcocks - correct?

    It must be tight - any tips?

  8. ThatXS650Guy

    ThatXS650Guy More Sparky than Speed Racer

    They actually clear the carb tops OK if you shim up the back of the tank about 10mm. I did resort to using a 90 degree brass fittings just after the petcock to ease out the fuel line kinks. Otherwise, no issues... You can even use the same lock from your stock tank so your keys match. It's a big improvement over the tiny Special tank. I can go 160 miles before I hit reserve.
    From this view you can see the barbed fittings and the high tech spacer. The dampner is the stock 750 item
    MaxPete likes this.
  9. MaxPete

    MaxPete New knee installed but still breakin’ her in.... Top Contributor XS650.com Supporter

    Cool - thanks Jim!

    I figured I'd need those 90 deg. spigots so I bought some already.

  10. aldo5468 has some pics of puck placement somewhere on this forum.

    I used the xs650 rear tank rubber on my conversion and I then carefully marked where the pucks would mount. The new mounted pucks clear the top of the stock gusset mounted cups by about 4mm, and the swing of the forks stop short of hitting the new tank by about 5 or 6mm on a full turn.

    There's a small section in the 750's tunnel that can use a bit of peening for clearance, Clarence........and as noted the stock seat pan needs to have about two inches removed from its forward end to clear the side hinged seat. I'm thinking a lift off seat may be getting real close to where the front securing fork mounts to the seat pan if trimming two inches off.
    MaxPete likes this.
  11. You can take 1 3/4" - 2" off the nose of a lift-off seat and not lose the front securing forks. I can't remember now exactly how much I had taken off, but it was in that range. In retrospect, dunno if I'd do that conversion again - the 750 tank is enough larger to make the bike look a bit top heavy. Probably go for a Standard tank if I had it to do over.
  12. 650Skull

    650Skull Dogonit Top Contributor

    First link post #3
  13. SDLars

    SDLars XS650 Member

    Is there a way to tell from photos of it is the standard or the special? I see lots of specials available.
  14. 650Skull

    650Skull Dogonit Top Contributor

    Standard Tanks 74-79 have the cgas cap in the center of the tank. All Special Tanks have the cap to the side.
    Left; 74/75..Center 76-79. Right Special 78-83
    ........ P1000917.JPG

    74/75 Standard tanks have a raised cap and no side badges., No aftermarket cap alternative. If a tank for sale doesn't have the cap it is worth considering passing up on the deal. Used or OEM gas caps are very hard to find or very expensive if you do.
    P1000921.JPG 74TXA-75B.jpg

    76/77 Standard tanks have a similar gas cap to the specials. and no side badges. Aftermarket Caps available
    These standard caps look the same as Special caps but they arn't and do not interchange
    76C.jpg 76C   ..jpg 77D  Blue.jpg

    78/79 Standard tanks have the same gas cap as the 76/77. These 2 years have badges on the side
    79F..jpg 79F,,.jpg 78E.jpg

    There is a difference with the petcocks.
    74-77 have manual petcocks
    78/79 have Vacuum operated petcocks

    78/79 petcocks are wider at the base and taller than the early 74-77 petcocks. Note in the pics, (silver tank and dark tank with badge missing), the base of the tank where they sit, you can see the earlier Tanks protrude where the petcocks sit. Later Vacuum petcocks tanks are slightly recessed to accommodate the extra height in the petcocks.

    Early and late tank petcocks do not interchange. If someone has filled in the bade on the later 78/79 tank check the petcock mounting to determine what tank it is.
    Last edited: Sep 14, 2018
  15. MaxPete

    MaxPete New knee installed but still breakin’ her in.... Top Contributor XS650.com Supporter

    Useful dope Skull!


  16. SDLars

    SDLars XS650 Member

    That's just the kind of information I need. Thanks very much!
    MaxPete likes this.
  17. 650Skull

    650Skull Dogonit Top Contributor

    Added some petcock info to Post #14
  18. azman857

    azman857 '80 XS 650SG Rider Top Contributor

    How much gas do those XS 750/850 tank hold? I do love the style. I have a Standard tank on my Special. I like the extra gallon for the range it gives me..
  19. ThatXS650Guy

    ThatXS650Guy More Sparky than Speed Racer

    4.5 Gallons
    azman857 likes this.
  20. If one were handy with a welder, you could marry an xs650 tank tunnel to an xs750 tank body and get even more capacity.......

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