OK... here goes my description of the fishing line trick.
Take the O-ring and two pieces of fishing line about 12-16 inches long (in this case longer is probably better). Imagine if you took a piece of the fishing line and on one end you looped it around and tied a knot so that you would have a 16 inch string with a little loop (the size of a dime) on the end. Do this to both strings but make sure to put the o-ring in each of the dime size loops as you tie the knots.
So, now you have two stings with an o-ring in the middle. This o-ring can now be pulled and stretched by tugging on the fishing line.
Take one of the lines and slip it from one side of the bike to the other side, then reach over the bike and grab it. Now you should have one hand on each side of the bike, and o-ring should be in the middle where you are about to install it. Using the fishing line to guide the o-ring, put the bottom of the o-ring in its groove and start pulling the fishing line up in a way that it pulls the o-ring into position.
After the o-ring is seated in the groove, you can take some scissors and reach in there and cut one side of the dime sized loop that you tied. After cutting ONE SIDE of the loop, simply pull on the line and it comes out.
Don't forget to use a little wd-40 on the new o-rings to help them slide into the cylinders, after let the bike sit for 45 minutes so wd40 will evaporate.
Then top off with coolant and go riding.
1998 SHADOW A.C.E. 750 - billet mirrors, memphis fats, HD choke cover, 39t sprocket etc. etc. etc.