All right, back at it! I just wrapped up about a seven hour session of fiddling, and I'm finally done!
I started by building a little test fitting to make sure I had the wire designations (always hot, accessory hot, and ground) correct. It also gave me a chance to freshen up my soldering skills, but in reality soldering wasn't necessary if you didn't want to do that. YouTube showed me how to wire up the Sumitomo connectors. Having the connector with three longer leads on it let me be really sure what I was checking with my multimeter and it proved the info from Lakesrider and McQueen was right: red was always hot, white was accessory hot, and black is ground. (pic of testing rig included)
Then, I wired up the tachometer to a plug that matched the tach's wiring to that for the Scram. Of course, the colors weren't the same so I checked, and checked, and checked again before finally plugging it in to see if it'd work. (pic included)
Then, just to keep it interesting, I wasted about two hours. I did this by pulling the tank and wrapping the signal lead around the HT lead to the spark plug, putting the tank back on, and finding the readings were very low. So, I pulled the tank again and added extra wraps, and after putting the tank back on again there was no change. SO, off comes the tank yet again and I spend some time digging around the wiring diagram and figure out a way to tap into the ignition coil instead. Tank back on, fire it up, and NO CHANGE the reading is still way lower than what the C-reader is telling me. Quoting Chris Knight from the amazing 80s flick Real Genius "but then, in the midst of my preparations for hari-kiri, it came to me." I'd forgotten to adjust the tach for the thumper's 2revolutions-1spark sequence! I imagine I would have been fine with the original wraps on the HT lead if I hadn't been such a bonehead. But with it hooked up to the ignition coil, and that actually being the best source for the signal, I called it good and left it be.
With the tank back on (again) it was time to finish mounting the unit. I really didn't like the way the unit sat with the v-shaped mounting bracket included with it, so in one of the pictures below you'll see how I cobbled together a bracket with some steel sheet and a couple bolts. The bolts needed to be secured with JB Weld as the heads aren't accessible once the bracket is mounted to the tach (see included pic). I also included a couple rubber/metal bumper thingys I found at the hardware store to help the unit sit off the dashboard enough that I could still reach the programming buttons on the back of the tach once it was mounted. The JBWeld-ed bolts went through the mounting holes originally used by the Tripper, for a perfect fit. The long studs pictured needed to be cut off once secured.
With everything mounted, it was just a matter of tucking away the wiring and remounting the headlight. A brief test-ride shows everything works bomber and I'm VERY happy with how the install looks. I really think it looks stock, like it was this way from the factory. I've included a pic of the final results, I know the clocks are off by a minute (it bugs me too) but I'll get that hammered out later.
For those considering such a project: it was a fun and satisfying project but dang, it took some WORK. I really envy the Classic folks who apparently have a plug-and-play tachometer kit coming from Hitchcock's soon. The exploration and deciding how to proceed, waiting for the connectors, wiring everything up, brainstorming how to build the mounting bracket, and getting everything finally assembled took some serious time and many trips to the local hardware. Give 'er a go if you fancy it, but keep in mind this isn't going to be a "quickie project" that's done in short time.
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