OMS Ironhead Thumper : 03

This project has been sitting for a month or so. I figured it was time to move forward and get the rear wheel mocked up and on the bike. That one sentence took a week of after work free time to get completed. First of all the wheel that we had acquired with the project is a later disc brake wheel. In 1975 the Sportster came with a Drum brake rear wheel. I thought to myself “No big deal we have a caliper and a master cylinder to use for this.” So I went to bolt the whole assembly up and what I realized is the later disc brake wheels use 3/4” Id bearings and the original drum brake set up used 5/8 ID bearings. All the original hardware was useless as is. What to do? I found a 3/4” diameter axle and nut in a box of parts but it was 2-1/2” too long. I cut the head off the original axle and drilled a 1/2” diameter hole through the center of the head and cut the 2-1/2” inches off and turned a 1/2” post on the axle then proceeded to weld the head back on. Next on the hit list was the axle adjusters needed to be opened up to 3/4” also. I went back to the lathe with a boring bar to make short work of this task. The 3/4” axle needs to ride in a 7/8” slot in the swing arm so 2 spacers with 7/8” flats were made to center the axle in the slots in the swingarm. The last piece of this puzzle was a 3/4 long straight spacer. I found a chrome one in a box from a previous build. All of our work bolted right up and lined up the wheel and sprocket like it was meant to be there. Next on the list is to fabricate an anchor for the brake caliper to the swingarm.









We mocked up and installed the fuel tank. The tank it is one of the few new parts of this build so far. With the tank bolted on the coil and bracket was located and installed as well as the front and rear head with the rocker boxes. This is all temporary until we get the body fab work completed then the motor will come out for the cylinder modifications.

Tim