I found out the hard way, after my purchase that if you own a 2001-early 2005 GL1800 and you have a Motor Trike kit with the 3rd generation driveshaft, lubing the front u-joint is not going to happen. That is because the u-joint zero fitting is further back in the frame and no way to go straight in to lube it.
So after careful examination I thought, "Why do I have to go straight in?" I rolled the trike and positioned the zerk fitting pointed straight up. Now there is something that I can work on. So I got onto my computer and began a search for 90 degree grease couplers. After researching them all I concluded that this coupler might work for this application.
http://www.amazon.com/Lumax-LX-1404-.../dp/B000MS5T42
So I ordered my coupler and waited for it to arrive. Upon arrival, I took it apart and placed the 90 degree end onto my flexible hose of my grease gun, and almost like magic, it works. Now here are some things you need to do first before plunging into the cavity. After transferring the coupler onto your flex hose, use any zero fitting to "break in" the new coupler. The jaws of it are extremely tight and you need to do this, trust me. Next when you snake the fitting in place, either have someone hold a flashlight or use a shop light to see. Place the end of the coupler on top of the zerk fitting after rotating it straight up. Do this by coming in from the front side on an angle and rotate it straight up. There is not a lot of room under there, the starter is in the way. And finally use a long handled straight screwdriver to push the coupler onto the zerk fitting. When done just rotate it to the side, and use your screwdriver to pop it off.
Here is what it look like installed on the end of my hose:
Here is where I enter to get to the zerk fitting (under the right side transmission cover):
And finally here is the coupler on the zerk fitting, ready for action:
Sorry for the position of the photos, my IPhone rotated them.
I really hope this helps all of you in this situation. Please feel free to PM me if you have any concerns or questions.