Disclaimer: For anyone debating about doing the GSXR or similar piggyback shock mod - Don't do it, unless you have a LOT of time or free access to a machine shop to do the requisite grinding and cutting to make it fit. You're much better off using the time to find a shock with a remote reservoir.
Here are some notes from a member who put a 2006 GSXR shock on his Ninja. Since this installation will involve a lot of personal choice, tinkering, and fabrication, we'll let Silver explain his approach.
Please note that if you install a shock with a piggyback (attached, non-remote) reservoir, you will lose your airbox and have to move the battery box as well.
I ordered a 2006 GSXR600 shock, thinking that possibly the reservoir would clear the battery. I have been running an SV650 shock which, though for me it was better than stock, was nowhere near what I was looking for to match up with the .7 Sonic springs and the MT75 tires. The shock was $19.99 off of ebay and shows very, very little wear. I doubt this shock saw 100 miles. At any rate, I found that the res would not clear the bottom of the battery tray. I needed 3/4 of an inch or so to make it happen, and that is what I did. I do get ahead of myself though.
First, the shock. 12.5 inches eye to eye with preload, rebound adjustment and compression adjustment. Appears they are considered soft by the owners of said shocks, but had been mentioned as a possible replacement for the ex250. I also understand that replacement springs can be ordered and that the stock one is rated at 525 pounds.
1) Top eye. Too bad it is a tad small. I found I had to increase the diameter 1 mm. I did this with a sanding disc in the dremel. Round and round she went, stopping at no point until I felt I could press in the new ex250 shock fitting, which I got from Ron Ayers for ~$13.95. One problem solved. The top fitting width wise is spot on, so the top was done.
2) The bottom eye. Never liked the idea of bending the SV650 bottom mounts. If stiction did not come into play, then it was just bad form. Bottom eye had to be drilled out a tad, as the stock ex250 bolt would not fit. Easy to do with a drill press, and the aluminum was rather soft to a new drill bit. Plenty of material there. Next was addressing the legs, which where a tad narrow for the stock mount. A flat file and some patience while using a caliber to insure the offset was negligible and presto, a shock that mounts so tightly as to infer an aftermarket shock.
3) Cut out battery tray area of the fender but NOT the flange or supporting plastic for the mounting of the radiator reservoir. Dremel cutoff wheel and jig saw. Save the metal bracket from under the tray, as I mounted this to the homemade bracket, which we shall make shortly.
4) 1.25" x 1/8 x 3 feet or so steel stock purchased from Home Depot. Make bracket to match up flat with the shock top mount, curving over the shock res clearance area, then bend into the rear fender to tie it back to the shock mount. A lot of heating with a propane torch and hammering/bending to get the rough shape, then cutting it to length and further heating/hammering/bending to get the exact fit. Cut the shock-to-fender mount off of the existing shock mount, then cut the legs off of the face of the piece you cut off. You need the face to bolt up to the rear fender in a stock-like fashion, but it will now be attached to the new bracket you make.
5) I then used the dremel with the sanding disc to remove the paint from the top of the shock mount, and the inside bottom lip and paint from the existing rear fender mount that we cut off. I further ran the dremel on the steel mating areas that we were going to attach, then used acetone to wipe down these areas. I used JB Weld to attach both the fender mount and the rear of the bracket to the shock mount, along with C-clamps. This was done in two separate stages. First, the rear fender mount. Let it dry, then id and drill the mounting holes in the fender, which will allow the shock mount part to lay down on the shock mount. JB Weld this and use a C-clamp. Let the part dry well.
6) The metal plate from under the old fender battery mount. Cut off the rivets, touch up with dremel and acetone on both it and the bracket, then locate and JB Weld the bracket into place.
7) Some time ago I purchased a second air box off ebay, so I could chop it up to give me a better box for the stock location, using the stock rubber strap as well and tool tray. I cut this off the battery box and used JB weld to relocate the catch for the rubber strap to the face of it. This allowed the K & N's to be installed while making no changes to the battery/tool tray areas. This is the battery box that I used to make this shock install.
The important thing was to insure that the shock res had the play it needed, while the top posts of the battery did not exceed the top of the frame tubes above it and were preferably a touch below it. I did this well, but should have moved the battery forward 1/2 inch, as this would have made a perfect tool tray fitting, though it is still close to perfect.
The shock spring comes close to the swing arm pivot but never makes contact. The res has plenty of clearance and will never touch anything. All adjusters are accessible with the wheel on, though the preload is a touch tight (need to make an adjuster for the preload rings. Apparently the tool kits on the GSXR do not contain it.) I am going to leave it at the stock factory (?) settings for now and play as necessary.
8) The last item I addressed was the exposure of the shock at the rear fender, as I had cut out a section and there are areas on the shock I would like to keep from getting abused. Not having much suitable to use save for a windshield design I made this spring, which had a maddening habit of folding at anything over 90 mph, I cut it and fit it into the fender well, using sand paper and acetone to prep all areas. Then JB Weld along with a rubber band to keep it all in place till dry (24 hours). One Lexan protector for my shock.
Static sag was 6mm and rider sag at 28mm. I later moved the rider sag to 32mm. I weigh approximately 155 pounds ready to ride.
I rode the bike up and down the street a couple of times in order to check out the assemblage and any abnormalities in the bike. All seems well.
Total cost was $19.99 for the shock (plus $6 for shipping), one eye out of ex250 shock (though I did ordered 2 more at $13.95 I used the one I had). JB WELD $5 more or less I think and $5 for the steel from Home Depot.
I can say that the bike does sit down a tad when I get on it and rises a tad when I get off (something the SV650 shock did not do at full preload due to waging of the tail in corners). I weigh 150/155 fully dressed to ride. The height and angle feel good.
The shock is in, and I am very happy with it. Bumps are still there, though not nearly as severe, and cornering is flat and steady to the edge of the MT75s. The tires, Sonic .7 springs w/15w oil and the GSXR shock have the little Ninja cornering very well. It is almost scary how well it hugs the road now and in fact continues to dive into corners if you are not paying attention. Very fast steering, tires and suspension that keep the road solidly under the bike for a nominal cost.