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Fuel tank interchange information

Discussion in 'XJ Technical Chat' started by hogfiddles, Jan 29, 2017.

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  1. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    There are many questions on tank interchanges, so this thread is being created to address tank interchanges....from "drop-on-and-go", to "will work with modifications", to "doesn't work". Whenever possible, picture will be included so you can SEE the actual swap.

    I have already posted a lot of swap info in other threads, but I am going to try and compile it all here, so this will be an ongoing, and developing, thread.

    If you have a question regarding a particular swap, feel free to start a conversation with me.

    Dave Fox
     
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  2. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    XJ650 Maxim/XJ750 Maxim

    1980-1983 all interchange.

    The 750 Maxim tank is a direct bolt-on upgrade for the 650 Maxim. Some 750 Maxim tanks have a fuel level sending unit, others do not. Either way, the 650 Maxim does not use it......just wrap it up and tuck it out of the way.
     
  3. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    XJ750rj tank on XJ650rj non-turbo

    the '81-'83 xj750r tank will fit the '82-'83 650rj non-turbo Seca.

    The front of the tank will interfere with the horn assembly. Relocating that assembly will alleviate that issue.

    The rear of the tank does not line up perfectly with the seat and side cover, so you would need to find a creative way to disguise the strange intersect of the 'lines'.

    In the USA, this is the XJ650 Seca. in Europe, it is simply the XJ650 since they did not get the Maxim styling.

    image.jpeg

    image.jpeg
     
  4. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    XJ750 Maxim tank on an XJ650rj non-turbo

    Up-to-1983 XJ750 Maxim tank will physically fit on the 1982-1983 XJ650r

    Issues:

    -Tank bumps up against the horn bracket, relocating the mount would solve that
    -the overal tank cavity is shorter in length, so there is a major gap between the seat and the tank
    -The tail end of the tank is narrower than the 650r tank, so it does not flow into the covers, seat, etc.....


    image.jpeg

    image.jpeg

    image.jpeg
     
  5. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    1982 XJ550r on a 1982 XJ750r

    Ok so-- the 550r tank will just barely fit on a bare 750r frame, but is not a drop-on fit, for a complete bike. It's close enough to almost fit, but here are the problems:

    Trailing end of the tank doesn't 'flow' into the side covers.
    AND
    Side cover top mount has no hole to go into so the cover is loose. The 750r tank has a hole and bushing for this mounting post

    The tank mount rubbers are too thick, ad the tank can't slide into place.

    Removing the tank mount rubbers allows the tank to slide into the mount position, but then there's no isolation, and the tank rattles around them.

    BUT

    With the tank just sitting in this position...... Thee front of the tank interferes with the handlebar cover. Removing the cover will alleviate that issue.

    BUT

    The front of the tank interferes with the reflector mounts. If these are removed, that will alleviate that. I DON'T think it will move the tank forward enough to cause any more interference with the handlebars though force the handlebar cover is removed. It feels like there's enough space under the cover to avoid that issue again.

    BUT

    Unless the reflector bases are removed, the tank can not slide up the last centimeter, or so, to allow the rear of the tank to line up with the rear tank mount. HOWEVER, if they are removed and the tank is pushed as far forward as it go, then the tail can be finessed onto the rear mount.........the issue then is that the tank mount bushings at the front can't fit all the in anyway because the bushing cups on the tank itself are jammed tight up against the bushing mounts

    PLUS

    The rear of the tank is still elevated above the rear mount because the bottom of the tank is too flat near the end of the tank and it hits the frame before the tank is sitting down on the the mount. A good rubber spacer could be made for that........


    image.jpeg

    image.jpeg

    image.jpeg

    7 image.jpeg image.jpeg
     
  6. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    1983 XJ900rk/1984 XJ750rl
    These tanks are direct swaps for each other.

    Issues

    -none
    -only differences in tanks will be that some had hooks for the air scoops, and some did not.

    The bikes are basically the same bike. The major difference is that basically the 750rl is a 900rk but with a 750 engine. Virtually every other part is the same as the 900 with few differences.

    No picture is needed.
     
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  7. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    In the meantime, here's some general info minus pics. As I can take pics, I'll move the write-ups to individual posts as above...
    ..........

    Pulling together info that I have posted regarding tanks..... sometime I'll even re-write it to make a it a little more coherent and logical. Nonetheless, here's the info. Read through it, and maybe you'll find what you need:
    ------
    Just for giggles, I did swap some things around to see how things fit:

    1 900rk Tank- does NOT mount onto the xj650 maxim, xj750 maxim, OR xj750 seca frame. The upper mount for the frame reflector contacts the seam edge of the 900 tank before the tank can slide onto the rubber mounts. If the reflector mounts were cut off, the tank would slide onto the rubber mounts, BUT the tail of the tank would still be about an inch too far back and will still not allow the tank to be bolted down.

    2.750 Maxim tank - as we all know, the 750 maxim tank is a direct bolt-on swap for the 650 maxim tank. The 750 maxim tank WILL also bolt directly onto the 750 seca frame without any modification to the tank of the frame.

    The seca seat will still work on the frame, but there is about a 1" or so gap between the seat and the 750 maxim tank.

    The seca side covers will not mount onto the frame as the tail end of the maxim tank aims down at the back and interferes with the sidecover top-front edge.

    3. 750 seca tank - WILL physically bolt directly onto the 650 and 750 Maxim frames.

    The Maxim seat front edges need to be modified to fit the extra length and steeper angle at the rear of the 750 seca tank.

    I did not have time to check on sidecover fit. However, due to the upsweep at the rear of the seca tank, the maxim side cover upper front point should still be ok and not interfere.

    ---------

    Regarding 650 Seca / 650 maxim

    Frames are different, I haven't done a seat-swap comparo, but I have done tank-swap comparo which is here in another forum......

    That all said, if I get the time in the next few days, I'll try to do that for you.

    In the meantime, a quick solution would be to pull the covers and foam, and the do a Seatpan swap..... The seat mounting is different

    The 650 rj tank will fit the maxim frame, but you should use the 650rj triple clamps to allow clearance at the front if the tank.... Otherwise you'll run the fork tubes up against the tank on tight turns
    --------------
    650rj tank on a 550r

    650rj tank is slightly shorter in length, by about 1/4 inch at rear oval mounting hole. However, if the tank is pulled back just that tiny bit it will bolt into place. Doing that though, pulls the front hooks about 1/4" back, which leaves a slightly "loose" fit at the front.

    The petcock just clears the valve cover but with enough clearance to not be an issue.

    The bottom rear of the tank does interfere with the seat pan's lower front corners but they could be trimmed back and re-shaped a bit to allow the seat token and close again.

    The front of the seat is too long, too, but if it is cut back and re-shaped and re-curved I could be made to fit nicely.

    All that would be cosmetic changes, and readily do-able.
    The only "major" issue will be that the bottom of the cramped edge of the tank touches the top ends of the airbox. Once the tank is bolted down there will be pressure in the airbox. If the airbox is heated and softened, the two "channels" could be formed. I guess the tank could be trimmed, but I think that may weaken the seams and I wouldn't recommend that.

    550r tank on the 650rj

    The 550r tank is about1/4" too long, PLUS the front mounting grommets are just a little bit too wide for the tank to slide on.

    When the grommets were removed the tank almost fits right in place.

    However, the lower front edges of the tank interfered with the horns. If those are lowered or relocated, that issue will be easily resolved.

    The rear of the tank tunnel interferes with the frame but if the tank rear is raised about an inch or so, it clears the frame. If some makes a riser/spacer to mount the tank just that little bit higher its right in line above the regular rear mount

    The issues to really address would be --what to do about the tank grommets on the 650r, and the rear mount. Here are the solutions....

    Two things must be done for the front:

    1. The big ring on the mount needs to be moved in toward the backbone about 1/4" on each mount to allow the rubber grommets to fit in the slightly narrower tunnel of the tank.

    2. Use the grommets from the 550r, as they are slightly less tall AND the have a little bit smaller diameter that the 650rj grommets.

    For the rear of the tank--make spacer to mount the end of the tank about an inch or so higher above the original mount.

    Long and short of it:

    Either tank can fit on either bike with either seat mods and airbox mods to put a 650r tank on a 550r; or, minor alteration to the front tank mounts on the 650r, relocate the horns, and add a riser for the rear mount will allow the 550r tank to fit on the 650r

    Dave Fox
     
  8. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    XJ1100 tank on an XJ750 Maxim/XJ750 Maxim tank on an XJ1100

    I have had a few inquiries regarding whether an xj1100 tank could be an upgrade to the 750.....Sad to say, it is not. The 1100 tank is MUCH bigger, and the tunnel is much WIDER. If you have a lot of money, and want to do a lot of custom work, I guess you could make something happen, but it's definitely not a drop-in swap. Also, the plumbing for the Xj 1100 tank would be different.....there are two petcocks to contend with.

    It would NOT be an upgrade to try and put a 750 tank on the 1100, either. First, it won't fit because the tunnel is too small; second, the 750 tank is way too short; third, you'd have LESS fuel capacity.
    From the start, you can see a substantial difference.........Xj 750 Maxim tank on the left, Xj 1100 tank on the right
    image.jpeg

    A peek underneath....again, xj750 Maxim tank on the left, xj1100 tank on the right.
    image.jpeg
     
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  9. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    XJ750rj tank on 1983 XJ650 Maxim

    The 750r tank will physically bolt right onto the 650 Maxim frame. But, while it will physically fit right on, there is a little work tat will need to be done.

    The seat is slightly too long in the front. Specifically, the 'rise' at the front of the seat is too far to the front to allow it to drop back into place. The seat will fit into the area if you take some time to address it. The front of the seat will need to be trimmed back, the pan will need to be reshapced a bit to work around the tail of the 750r tank. My recommendation is;
    1. take the seat cover and the foam completely off
    2. install the seat pan into position and lock it in place. Trim the front lip as needed.
    3. set the foam on top of the pan, as close to in place as you can get it.
    4. Take your time and slowly trim the foam back and shape it as needed
    5. Re-staple the cover

    You will need to get creative if you wish to cover the funny-looking areas where the tank/cover/seat meet.

    The tank clears the triple clamp and handlebars
    The side reflectors clear the tank by about 1/8"

    1983 XJ650 Maxim w/750 maxim tank
    IMG_2123.JPG

    XJ650 Maxim w/750r tank
    IMG_2124.JPG

    Sits perfectly on rear mount, but raises the top line of the tank to interfere with SEAT FOAM.
    IMG_2127.JPG

    Perfect fit on front mounts
    IMG_2130.JPG

    Clears triple clamp/bars/forks
    IMG_2128.JPG

    Clears side reflectors, easily - but not by much.
    IMG_2131.JPG
     
    Last edited: Dec 4, 2017
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  10. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    XJ750rj tank on an XJ900rk(XJ750rl)

    The tank physically is close, but would take extra work to make it half decent.
    IMG_4657.JPG

    There is a big gap at the front of the tank
    IMG_4658.JPG

    The seat physically fits, but would have to have the plastic pan re-shaped at the front. Heat the plastic and bend it out....
    IMG_4659.JPG

    The rear corners of the tank, the side covers, and the seat do not meet well at all.
    IMG_4660.JPG

    The rear of the tank is awful close to meeting the mounting point, but is about an inch or so shy, and even with the rubber cushion removed, the tank does not sit down on it. The tank is slightly to narrow.... I'm sure some careful hammer-work would solve that. The other issue is that the wire pigtail from the sending unit is right where the frame wantsto be, and it pushes the tank a bit to the left. When things are removed, and the tank is pulled back far enough to sit on the boss, the tank still does not clear the frame, and the front mounts are just about off of the rubber cushions there.
    IMG_4661.JPG IMG_4663.JPG IMG_4664.JPG
    So, the long and short is that it's close enough to be possible with some extra thought and work. But, it is not a drop-in replacement or upgrade.
     
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