Tapping the Headstock and the swing arm I first saw in a post by JerryHawk250. I like to be able to pump grease in for maintenance and as back up for water dunking. It does take some mechanical skill and special tools. You can also just take the swing arm apart, clean it, and repack with grease.
I marked the location of the grease zert when the bike was still sitting on its wheels. That way I could angle it best for using a grease gun.
A special tapping wrench to hold the tap helps much in this tight space. TIP: Get a tap and die set from Harbor Freight or just buy the handle tool. For years I did it with a small crescent wrench.
anger smileys
The thickness of the swing arm and the bearings on the end is about 5mm plus a little. The spacer/bolt tube rides on the bearings on the end. There is a small space, 2 mm so (thickness of the bearing that exists between the spacer and the swing arm where grease can reside and also be pumped out to the bearings on each end. The ZERT is tapped only through the swing arm itself so it can put grease in the space between. A standard ZERT may work but it may hit the tube or puts the end right against the spacer. I took a file and filed off several MM to gain space for the grease to enter, but before I filed it I put grease in the end of the ZERT to keep filings for dropping inside. This pix shows a shortened 45-degree angle ZERT. I cut off a straight one with a hack saw and you see what happens.
The spacer/bolt tube cleaned up but still bears the scars from the rust. I used some 400 and 600 grit sand paper to clean it up. I only want to reduce the diameter of the tube as little as possible to keep the best fit. The tube rides on the ¾ inch wide bearings on the ends. The pitting is just another place for grease to reside.
One issue I had to resolve was how to get grease to the inside of the spacer/bolt tube around it and the swing arm bolt because it needs lubrication too. I decided to drill four ¼ inch holes in the spacer, two on each side of the ZERT to see if I can get some grease to pump into the bolt cavity. The spacer fits pretty tight with just a little play. Looking at it today, I may put another hole right in front of that grease ZERT. When I grease it, I will first grease everything by hand, especially the bolt and inside the spacer/bolt tube. Then pump grease in to take up any air space.
The swing arm tapped. Needs a quarter turn (and some thread locker) and I will do that when I do final installation.
I updated the above post on the swing arm to include the specifications for the spacer/bolt tube. Re-installation is pending some other rear end work. I am glad I got this swing arm issue straightened out!
Trivia: What inexpensive Chinese motorcycle comes from the factory tapped with a swing arm ZERT? If you know the answer post it up!