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!

Dallas to LA, now past tense!

i picked up the old Yamaha from where it had sat in my sister's garage in Dallas, TX, and knocked out the next leg of the saga: Los Angeles, CA. i didn't do any blogging, but here's an email I sent after the ride's one mechanical adventure.

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Yes, if there was ever a situation involving a leaking gas tank that had a good chance of being spectacular, this was f'n it. So full of lucky coincidences that it's deliciously divine.

So ZERO problems with bike for over a thousand miles. Nothing. And very little exposure, too. Route 66 gift shops and service stations every 2 miles, and I40 is so well serviced I only started to think about where to get fuel once I was well into reserve and had about 15 miles left. Easy livin'.

Given all this, I merely shrugged as I headed into the Mojave and blasted past a "no services 58 miles" sign. A little into this gap, I had an urge to troubleshoot a little high-rpm stumble that had been with me the whole trip. I reached down to jiggle the #3 plug wire, pretty sure the problem was thereabouts. Alas, the thing breaks in half, and the plug boot part whisks into the slipstream and vanishes. Shit! The bike wallows down to about 45mph at full throttle and I angled towards the shoulder. Out of service.

That must have been the best of the three cylinders, because the thing wouldnt even idle or restart with the remaining 2. Super out-of-service. Luckily, the bare end of the spark plug wire reached the spark plug, and I lashed it there in place with zip ties. With a visible and audible crackle as the spark jumped the gap to the plug, the bike started and purred. IN SERVICE!

Just as I was about to pat myself all over in congratulations, I became aware of a dripping and sizzling sound that had been going on in the background the whole time. I walked around the bike, and saw a steady trickle of gas running out of the lower seam of the gas tank onto the engine. WTF!? Really? The ONE spot on the trip 40 miles from services and with no cell coverage?

I fiddled with duct tape and electrical tape, but ended up wedging in some folded up paper between the tank and motor and slowing it to a steady sizzling drip. Based on some quick estimations of drip rate and distance, I figured I had a good chance of making it as long as I didn't stop anywhere too long.

Two things occurred to me as I swung my leg over:

1) You couldn't design a better fuel/air bomb. The hot motor instantly vaporized the gas into a dense, shimmering fog, and there was an open, exposed, hot blue spark right on the other side of the bike. Perfect.

2) If I hadn't had the urge to fiddle with the spark plug wire, and if it hadn't broken in half, the fuel would have continued to stream out unchecked as I rode, and I would have completely and unexpectedly run out of gas in the middle of the one hugely exposed part of the trip. I would have been truely and completely stranded, trying to flag down truckers or stand on rocks to try and get cell coverage. Amazing luck.

Well, I did make it out of the Mojave with over a gallon of fuel left. By best accounts I leaked more than half my tank. I'm writing this because I have nothing else to do while the JB-weld cures.

Hope you don't mind, I'll add some pics and make this my only blog post of the trip ;)