Sunday, October 4, 2015

Diesel Land Speed Racer Mk2 - Part 6 - Starting and Stopping

The engine in the Diesel Sportster is 3 times larger than the engine in my first bike, so it requires an electric starter and a fuel pump to operate correctly. It also has a heavy-duty solenoid that holds the governor open, and snaps closed to shut the engine down when the kill switch is used. These are all relatively high-amperage systems, so a single fuse and normal switches were not enough to safely control them. 

For the electrical system, I used a marine-grade 6-fuse block and a pair of automotive relays. The fuses protect every individual circuit which will simplify troubleshooting, and by using relays I can avoid sending high amps through the relatively fragile handlebar switches. All of the wires are color-coded, with yellow wires for the starter system, white wires for the governor solenoid, red for main power, black for control switch power, and green for ground.

The fuel pump is another marine-grade unit which is rated for most types of fuel, including biodiesel.

Now that starting was done, it was time to focus on stopping. The original Harley calipers suffered an extreme design flaw. The bolts that held them to the swingarm screwed into nuts that were captured in hexagon-shaped holes in the alloy caliper body. Unfortunately, when these need to be removed and rebuilt, the bolts have inevitably seized from rust and the nuts tear open the hexagonal holes, wrecking the casting and making it impossible to tighten the bolts correctly during reassembly.

The caliper I purchased (for cheap) of course had been discarded because of this damage. I drilled out the old shoulder bolts, milled the hexagon holes round, installed steel spacers to keep the new nuts from gouging into the alloy caliper body, and installed modified 7/16 diameter socket-cap bolts and locking nuts.

NOS replacement bolts, which were unusable because the chrome was flaking off.

Final installation.