Systems, observation, and motorcycles

Our family spent a bunch of time this weekend cleaning out the garage and taking care of a variety of long neglected household tasks. One thing I’d been meaning to do for over a year now is to get my Ducati up and running again. Between picking kids up (need a car for that), and riding my bike to work most of last summer, it’s probably been 18 months since I started the thing. Keep in mind, that Ducati’s are fickle machines to start with, but I figured I’d work on it for a while before calling someone to load it on a truck and haul it to the shop.

The first thing I did was drain the gas tank. I couldn’t recall if I added fuel stabilizer, but after that long, I can pretty much guarantee that the fuel was bad. I took the bad gas to the hazardous waste site (open on Sunday from 9-5!), picked up some new fuel, headed home, and gassed the Duc up.

I had the battery on a battery tender, but was still slightly surprised that it still had some starting power in it. Unfortunately, the engine just wouldn’t turn over. I double checked the fuel line (clear) and then pulled the spark plugs. The plugs were a little dirty, so I swapped them with a spare set from the toolbox.

Still nothing.

Sitting on the bike, I took a moment to think through how the engine worked. The starter was working, gas was flowing, but the engine wasn’t starting. Fortunately, I have a carbureted engine, and know what all (or most) of the engine workflow. There could still be bad gas still in the system, or there could be a problem with the carburetor. But neither of those seemed likely. I tried starting it one more time, and the engine just wouldn’t kick in.

While thinking through it some more, I noticed that I forgot to reattach one of the spark plug caps. I reattached it and…still nothing.

But – the behavior (i.e. engine sound) was identical with and without the spark plug cap attached – which pretty much guarantees that the spark plugs weren’t firing. I took them out one more time, cleaned them, and this time, checked the gap. For some reason, my spares were gapped really narrow (hint – always check the gap – even on brand new spark plugs selected for your vehicle). I widened the gap a few millimeters to spec, put them in and…

Vroom!

I immediately grabbed my helmet and gloves and went for a spin, and the bike ran great. No stalls, backfires or stutters. It probably still needs some more air in the tires and an oil change, but it sounds and runs just like a Ducati should.

In the end, this was just another debugging and diagnostic problem – much like the problems I face almost every day. The key points to remember are:

• Know the system, and think about the system. When software (or Ducatis) fail, think through the entire system to note where failures may be occurring
• Observe what’s going on – Products (and engines) fail for a reason. Chances are that there are unnoticed clues to the behavior you are seeing, so remember that anything you see may be helpful.