So, I went to start Spinal Tap on Saturday, to take it up where a local shop had a portable dyno brought in, so I could get the AFR checked and get my new S&S Super E figured out. The setup: HC pistons, working decomp system, Dyna 3000, 4 ga wires on both sides of battery and from the start relay to the starter, new(ish) start relay (the new-style with heavy-duty contacts), Warrior starter, new(ish) Drag Specialties high-perf battery. I suspect the battery is a Yuasa in disguise. The battery was down a bit from only running a mile into town and back for Bike Night Thursdays, so it hasn't been getting fully charged. The carb is way off, it idles well and accelerates like a bat out of hell, but misses at steady speed. Anyhow, Spinal has always been hard-starting, which is why I got rid of the Weber 2bbl and went with the S&S.

As I was saying, I went to start it, but the battery was down. So, I got out the jumper cables, and hooked up to the battery in my car. This got the engine turning over, but it wasn't firing well. Suddenly, it fired against itself and stalled out the motor against the starter. This is the time when an electric motor draws the most current, and if you haven't glued the alternator rotor in place, when the Dreaded Starter Spin will occur. Since I recently did glue the rotor in place after getting Starter Spin, instead what happened was that the starter relay contacts welded together again! I had to emergency-disconnect the battery and go for a long ride on the working bike...

So, today I decided to fix this damn starter relay problem once and for all. And here's what I did:

I went and bought a Ford starter relay for about $20. I wanted one that was both ultra-heavy-duty and physically configured well, so I got one for a 1990 Crown Vic. This relay has an 'S' terminal which is one side of the relay coil, an 'I' terminal which is not used electrically, 2 main terminals which are the contacts for the battery/starter motor, and the other side of the relay coil is the mounting bracket of the relay (it grounds through the mounting flange when used in a car). The relay coil takes 3.07 amps when it's hooked to a battery, per my meter.

Since the start relay coil is operated by the contacts in the Main Relay Unit, and those are only rated at 2 amps (which I know because I have an old one I took apart, and it's printed on the inside), I had to find another way to operate the Ford relay. I went to Radio Shack and spent like $4 or so on an ultra-small 12v relay with contacts rated at 10 amps, and the coil uses .03 amps to operate.

Since the Yamaha start relay also provides the main 30 amp fuse a place to live and the connections it uses, I bought a 30 amp weatherproof fuse holder at the same time as the Ford relay, for like $5.

To hook all this together, I took the Radio Shack relay coil and soldered wires to it, and connected them to the red/wht and the blue wires which are in the small connector originally attached to the Yamaha start relay. This allows the normal start circuit to energize the small Radio Shack relay. I then soldered wires to the C and NO relay connections (Common and Normally Open). The C wire went to the giant lug on the Ford relay where the battery <+> was going to get attached. The NO wire went to the 'S' connector on the Ford relay. When the Radio Shack relay is energized, this puts +12 onto the 'S' connector to energize the Ford relay. To complete the Ford relay coil circuit, I used a machine screw and nut to attach a wire to the Ford relay mounting flange, and ran that wire back to the battery <-> post.

I attached one of the fuseholder wires to the same post that the battery <+> was going on, and the other wire to the 2 red wires in the connector that was formerly attached to the Yamaha start relay. Since the fuseholder had a mounting ear with a small hole, I bolted it to the unused 'I' post on the Ford relay.

I then attached the 4 ga wires to the giant posts on the Ford relay. Since the posts are bigger, I had to drill out the holes in the terminals so they'd fit. To mount everything, I removed the plastic deal that has the start relay, fuse box, etc. I removed the old Start relay, and cut the shoulders off the plastic ears that it was mounted on, on the outside parts. I also had to cut a pie-shape out of the bottom of the ears, so the body of the Ford relay would fit. I slid the Ford relay into place and drilled a hole through the other Ford relay flange mounting hole through the plastic tray and bolted the Ford relay into the tray.

Everything slid back into place, and looks like it belongs there. The stiff 4 ga wires were a bear to get in place, but once installed they were no longer a problem...

I tried it out, and Spinal Tap started up no problem. I think this may be one of the better starter mods based on how Spinal turned over, but time will tell. It certainly beat paying $55 for another "heavy duty" relay that only lasts for a couple dozen starts! I don't know how much a Ford Crown Vic start relay is rated for, but I bet it's WAY WAY more than the Yamaha relay!