CJ750 toolbox
Driveshaft elastic coupler repair by Terry Iseli

Last fall I had a little mishap with my drive train. While traveling down hill, at a speed approaching 55 mph, the rubber disc in my drive shaft suffered catastrophic failure. I knew this part was getting weak but opted for the “don’t fix it unless it’s broke” option. I had missed a very important clue that it was getting so close to failure. I had noticed rubber “spallings” on the left side of the sidecar. These bits of rubber were being thrown from the coupler disc. So, my word to the wise, if you see bits of rubber appearing on your sidecar...get the replacement part.

I contacted Long River Motorworks for the part, and researched the Toolbox section of CJU and files/past posting from CJE. I have also purchased parts from the CJ Parts Depot and from Mike from www.Blitzbikes.com in the past as well. After receiving much assistance and information from the group I wanted to write these instructions to give a little back. You can see from the photos that my CJ is not a “showroom” model. She may not be the prettiest girl at the ball but I love ‘er anyway. I use it for reenacting and to run about town and country roads. Some of the pictures were taken from below the bike.

I started by raising my Chang with an automotive floor jack at the sidecar frame near the rear coupling.
Then I placed a motorcycle/ATV jack with wood blocks to support the frame. This was necessary as the pipes are lower than the frame; this also provided much needed stabilization of the rig.
The next step was to remove the rear wheel. I removed the nuts that secure the supports for the rear fender, which was then raised and secured using a bungee cord/tarp strap hooked around the rear set hand loop. Next I removed the cotter pin from the right side axle. Then, using a 19mm socket, I loosened and removed the Colles nut and washer from the axle.
I next loosened the pinch bolt on the left side lower end of the shock using 17mm socket & ratchet, but a wrench or crescent/adjustable wrench would also work well. Then I placed a punch (a screwdriver or small bar/rod would work as well) through the hole in the left end of the axle and supported the rear wheel. I lifted up on the motorcycle tire with a block and an old section of leaf spring. I used the punch/rod to turn the axle and pull it out the left side of the bike. Whatever you do, do not tap on the threaded end of the axle. Tapping or hammering on the threaded end may damage the threads. I pulled the wheel off the drive splines and removed it from the bike. See Ross Kowalski’s post in the Toolbox section of CJU for an excellent example of this process.
At this point I referred to a post on CJE from Gerald Gardebled on the removal of the Final Drive. To do this, pull the cotter key and cross pin from the rear end of the brake rod, then lower the rod.
Remove the nut & washer on the lower frame of the right side plunger/shock and remove the tail pipe.
Also loosen the nut/bolt at the top of the plunger/shock...
...and remove the top cap from the plunger as well.
Now grasp the rear of the bell housing with your right hand and the front of it with your left.
Push with the right and pull with the left to disengage the drive shaft from the motor.
Go back to the right side plunger, or right rear shock. It’s clamped in place by a center “pipe” that is clamped in place by the frame. With the pinch bolt loosened and top cap removed, drive the center pipe up until it clears the lower frame.
I did this with a brass punch & hammer. Once the center pipe is clear of the lower frame, move the final drive to the rear, left and down. This will then allow you to remove the final drive and shaft from the bike.
At this point I removed the old disc. In the picture you can see the old part next to the new one.
When the disc flew apart, the pins on the propeller and the pins on the shaft came together. I do not know if this is common, but the pins on mine have a flat section on them. These sections are positioned so that without the rubber disc, they match up. Unable to get a trailer, I was able to “limp home” at 20 to 30 mph, for fourteen miles. I found no noticeable cracks on or around these pins.
I was also pleasantly surprised when I discovered the design of the coupling. The propeller has a center pin, and the drive-shaft has a center “cup”, which kept the shaft from completely flying apart. My respect for German engineering, and the Chinese for not changing the design, increased upon viewing the damaged part and the design of the “coupling”.
The next phase was by far the hardest. I discovered the pins in the drive train were just slightly larger than the holes in the disc. I used a very small amount of grease on the holes in the disc then applied pressure, alternating from side to side. I started by putting it on the propeller from the motor. Initially I used a pair of water pump pliers. (Do be sure to use a flat piece of metal or wood to protect the rubber.)
Once the disc was started enough to keep it on the pins, I used a small C-clamp to press it in place.
The final drive and shaft are then set back up into the frame. To do this, place the top portion of the plunger pipe up into the frame and rest the bottom end on the lower frame. At this point the bell housing is still turned inwards and the shaft “flexed”. Take care to keep the final drive from falling out onto the floor. I was able to wedge the lower portion of the plunger into the lower frame, but would’ve done better to secure it with a bungee cord.
Once the drive shaft pins were lined up with the opposing holes I used water pump pliers again to squeeze the pins into the disc. As with the installation onto the propeller,
one must alternate from side to side and use a flat piece of metal to protect the rubber. Once the pins were in well enough not to slip out, I switched to the C-clamp.
As this was done, the drive shaft came into alignment with the bike and the plunger pipe was able to slip into the frame. Although there was not much to this, it took some time due to having to alternate pressing/squeezing one side then the other. Little by little it came together.
I did find it necessary to move the hand shifter from time to time. This may not be the prescribed method, but I found it helpful to have the shaft in gear while I was doing the “pressing”. This way it kept from rotating at the wrong moment.
I also did this repair with the sidecar in place. I felt it was safest to do it this way without having to worry how to secure the “solo” bike in the upright position, although I imagine the bike could have been secured to the motorcycle/ATV jack.
Naturally once this is completed, one needs to work in reverse order to return the bike to operational status. Once the bike was back together and all the fasteners tightened, I took it on a dusty 14 mile cruise. Well after a little spin around town that is.
My thanks to all that have left information. I hope in some small way this can repay them and help others.