750 Tank Swap - Front Mounts - Another Way

aldo5468

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The first way I tried attaching the 650 tank dampers to the front of the frame was with a 1/4" bolt through the neck gussets using washers to clamp the dampers against the gussets. I had seen pix of this method either on this site or XS-650 Garage. I found that this allowed the tank to rock slightly side-to-side, and it just didn't seem to be the best way to transfer the tank weight back into the frame.

Being naturally cheap, I bought a couple of 3/4" copper pipe end caps, drilled 1/4" holes centered in their ends and shortened them with a tubing cutter to sit flush in the pockets in the dampers. I had to enlarge the pocket diameter a bit so the caps would slip in without distorting the outside diameter of the dampers - just wrap some coarse sandpaper (60 grit) around a socket that nearly fits the pocket and twist. Takes awhile, but eventually enough rubber abrades evenly around the ID to get the pipe cap in. Very solid now.
 

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thanks Aldo for the copper cap trick. I did the same this week and took a few more pics and dimensions to help the next guy.

I also found this good thread with pics of the process:

http://xs650temp.proboards.com/index.cgi?board=project&action=display&thread=4820

... and then took a few of my own. The first through hole I drill was too far back but the second just right. I used a marker to spot the tank pockets but the rubber disks just wouldn't go in deep enough. I used a drill guide block to get a straight through hole.

I first used a Dremmel cut off disk to cut on the rear tank mounting tab, at the obvious bend line. After cutting the slices, I used a rubber mallet to gradually bend the tank tab flatter. I ended up with the tab to tank flange edge being 15/16"

For the front through hole, I drilled it 13/16" down from the frame top tube or 1/4" from the top of the reinforcing plate. With a scale flat against the same plate, the centerline of the hole is 2 5/16" back from the steering stem tube.

The completed job is level with good clearance to the top tube when bars are at their stops.
 

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Very nice work! I had seen the thread that you included - it helped me to get started. I notched both the short flanges at the sides of the rear mounting tab and the sort of semi-circular pressing in the middle to bend the tab - I ended up with pretty much the same distance from tab to tank, and my painter welded in all three notches to restore the beam strength in the tab. I did not remove the original 650 front mounting "ears", since they did not interfere with the new, "higher up" mounts for the 750 tank.

Just to add to the "lore" - I found that the carbs blocked the petcock fuel outlets if the rear tab with the damper inserted was right down on the original mounting surface on the bike frame as shown in the thread you mentioned. My painter fabbed a 7/8" tall "riser" that fits down over the vertical "post" on the bike frame with a triangular plate welded at its top to support the damper. This raises the tank enough so that you can plumb the petcocks across the tops of the carbs into a T fitting that leads down to the carbs. I cut a nylon bushing to fit inside the hole in the damper, about 1mm shorter than the post to allow some compression of the damper; it sits on top of the post, and everything bolts down solidly using a longer-than-stock bolt.

If you want to add knee pads for a nice finishing touch, check out techspec-usa.com. See the tab entitled "General sheets" - they offer 3 patterns of material. I made a paper pattern using the original striping on my tank before it was stripped. Techspec material is a bit pricey, but looks sharp and made in USA.
 
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Thanks Guys!

Sorry to hear about the stock petcocks not working though ;-(
I can setup a riser block but more work to do ...

Yes, familiar with the tank pads. I have the "snake skin" pattern on the air inlet box and frame rails on my Buell Ulysses and really like them.
 
This is great. Thanks for the killer write up. I'm at the stage where I am about to cut off the cups. Is it possible to remove them without totally destroying them?

What is te trick to get them off? I understand they are welded on with a few spot welds and if I dril them out, the cups will come off. True?

Thanks.
 
Hi QWERTY,

Probably the best thing to do is not cut the original cups off. The PO had already ground them off and I finished the job. You can see from the rubber pucks that the 750 tank needs them higher than the 650 and should clear fine leaving them in place. Others have said so. I would have preferred leaving them on myself.

The cups are tacked solidly in three spots that you can see from one of my pics above. You could probably carefully use a hole saw to cut around the spot welds but then you'd have the cups with three big holes in them.
 
No need to remove the original "cups"; they do not interfere when installing a 750 tank on the new mounts and are hidden with the tank in place.
 
thanks Aldo for the copper cap trick. I did the same this week and took a few more pics and dimensions to help the next guy.

I also found this good thread with pics of the process:

http://xs650temp.proboards.com/index.cgi?board=project&action=display&thread=4820

... and then took a few of my own. The first through hole I drill was too far back but the second just right. I used a marker to spot the tank pockets but the rubber disks just wouldn't go in deep enough. I used a drill guide block to get a straight through hole.

I first used a Dremmel cut off disk to cut on the rear tank mounting tab, at the obvious bend line. After cutting the slices, I used a rubber mallet to gradually bend the tank tab flatter. I ended up with the tab to tank flange edge being 15/16"

For the front through hole, I drilled it 13/16" down from the frame top tube or 1/4" from the top of the reinforcing plate. With a scale flat against the same plate, the centerline of the hole is 2 5/16" back from the steering stem tube.

The completed job is level with good clearance to the top tube when bars are at their stops.


maybe I missed something but why are there two holes drilled for front mount in your pics above glennpm? Was one "practice"?
 
Yes, the first holes were too far back. the measurements worked but I couldn't get the rubber biscuits far enough into the cups. the dimensions I gave are for the correct location. Also as noted you don't have to take the original cups off of the frame.
 
I used my stock 650 rubbers and just converted them over, they converted over with out a hitch. My 750 tank i found didn't come with stock petcocks so i cant help you there.
 
does anyone know if the 750 tank conversion has enough clearance for the upper motor mounts?
I had no problem clearing the upper motor mounts. My sense is that the width of the "tunnel" under the 750 tank is greater that the one under the 650 tank.
 
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