Tehnical Recap- Preparing for the final leg from LA

I arrived at Chris and Katy's place and relaxed, ran, and dined out, ignoring the looming task of getting the motorcycle started for one last leg. It's getting harder each time. When I finally did get to it, it didn't go well. This is one very tired bike, begging for a bullet: compression is specified as 120psi minimum. The cylinders rolled in at 78psi, 60psi, and 30psi. It's amazing that this thing even starts. Oh, that's right. It won't. Yet.


It also has some pretty severe ignition problems. With the help of my 20Mhz 'scope I just happened to bring along (I don't have a screwdriver or a 10mm wrench in the tool kit anymore, but I do have an oscilloscope), I was able to identify a particularly weak coil that only reliably fires between about 1500 and 4000 RPM. I relocated this bad coil to be paired with the worst cylinder, and the two can just cuddle together in their lame suckiness for the rest of the trip. That change (and a very large hill near Chris' house) woke the XS750 from its slumber for one more ride.

Worried about startability, I worked the rest of the day hoping to find something worth fixing. I checked valve clearances, hoping to find a propped-open exhaust valve, went over the ignition system twice more, and did a quick shake-and-blow-out overhaul of the carbs. Nothing helped. This bike is just 145 years old in human years.

This morning, it passed the only roadworthiness test necessary for this trip- it started cold without a hill or starting fluid. We're good to go!