First off, I have to say that ANY upgrading of your scooter or repair for that matter if done incorrectly or with the wrong parts can be very DANGEROUS. So I recommend that no one do this conversion. Now on with the instructable...
I had read about the process for this upgrade years ago when I had my Elite 250, this process was taken from the Yahoo Honda Elite 250 Group and the tech tip from Randy Pozzi and Dennis Flora. It seems like you hit a bump and three miles later you are still bouncing along. It seems sensible that putting Honda CB350 shocks on your Honda Elite can be a good choice to improve handling, but the side by side comparison is shocking. The Elite shock looks like it is meant to hold up a hatchback rather than safely keep you on your bike.
Step 1: Take Off Body Pannels
Remove the side panels of your bike. There are four steps that you need to go through. Disconnect the turn signals (two wires each side with a junction under the rear bumper). Remove the 12 mm bolt (hidden by the rear bumper)
Take out the screw (under the passenger foot peg)
Finally there is a peg under the passenger handle that just pulls out.
Replacing the screws and bolts where you found them can help keep them straight for reassembly.
Step 2: Remove Muffler
Remove the muffler by removing the 10 mm bolt to the bumper, the three 12 mm bolts around the muffler and the two 10mm chrome cap nuts that hold the muffler to the engine. This reveals the shock on the muffler side.
Step 3: Adapt Shocks
I removed the excess rubber bushing off the 350 shock that I got. The Elite 250 group suggested that you take 2mm off of both side but my shocks slid in without that. If I get binding issues I will revisit this step.
Next you have to adapt the upper end of the 350 shock to work with the Elite hardware. By removing the sleeve from the top end of Elite shock you can adapt it by wrapping electrical tape around it until It is slightly bigger than the hole in the 350 bushing. A little bit of grease should allow you to push your adjusted hardware snugly in place.
Step 4: Postion the Shocks
Slide your shocks into place and replace the top bolt from the Elite.
The bottom of the shock needs a longer bolt and nut than the stock bolt and you can't use the stock 350 one because it won't fit. Put the nut on and tighten it all up. Reattach the muffler and body panels and you should be good to go.
Step 5: Go Scoot!
My bike has a bit of a rattle when I start it however it goes away when I sit on it. I am going to try and track that down (I think the new shock is touching the air box). But even with a bit of a rattle the handling is like a different bike. Really solid. The seat is just a little higher, so if you are short this may lift the seat too high.