I’ve been making a lot of “cobbler’s son” jokes this week. Of the three motorcycles I own with unexpired tags on them right now, exactly zero are running properly. One of them is a 2003 Honda Interceptor VFR800 with 7,000 miles on it. I bought it from a friend who bought it from a coworked who slid it down Gallatin Pike a solid hundred feet on its left side and then parked it for four years. After I bought it, I fixed a coolant leak (radiator damage from the crash) and then took it for one ride before the rear brake started locking up on me.
And I parked it for roughly one-point-five years, before I finally became so annoyed with myself that I actually disassembled the rear master cylinder, found the problem, and fixed it. (Root cause: someone had reassembled the master cylinder incorrectly. I swear it wasn’t me.) And then rode it for about 30 miles, hoping that it was running badly as a result of being parked too long and there being a bit of water in the fuel. (Did I mention spending 30 minutes to get the fuel cap open? Parking bikes outdoors for too long is bad for them, y’all.)
The problem didn’t go away, which meant there was something deeper going on. I found cylinder #3’s exhaust pipe to be cold compared to the other three, which suggested #3 either wasn’t firing or was getting too much or too little fuel to ignite. Turns out it was the middle problem. Fuel-injected bikes that run badly and don’t tell you what’s wrong via the “FI” warning light have only a short list of potential problems. Three times, now (twice on customer bikes), I’ve had a Honda run badly as a result of the fuel pressure regulator’s internal diaphragm tearing.
Rather than just failing to regulate fuel pressure, this has the added symptom of dumping a bunch of fuel through a vacuum line and into the nearest cylinder. In the case of the 2002-2008 VFR800, this vacuum line runs into cylinders #3 and #4, which sure enough were the cylinders with fuel sitting on top of the intake valves when I looked inside.
In roughly one week, a new fuel pressure regulator will show up at the threshold, and a small fuel spill and 30-45 minutes later, I’ll have at least one bike that runs well.