2003 Honda VFR800 running problem

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.)

regulator diagramThe 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.

And maybe I'll replace the worst fairing damage from the PPO's crash?

Maybe I’ll replace the worst fairing damage from the PPO’s crash while I’m at it.

by Andrew | April 7, 2013 at 12:28 pm | Outside Work | 10 comments


10 responses to “2003 Honda VFR800 running problem”

  1. […] And then in the process of riding it, I discovered the bike hid a fatal flaw: Every time I rode it, I ended up stinking of exhaust fumes. Low speed, high speed, didn’t matter. I considered various ways to remedy the problem, then decided to sell it instead, after about nine months and 2,000 miles. Funny how one detail like that can scuttle the whole machine. Besides, I needed an incentive to finish my VFR800. […]

  2. Not only for Honda vfr800 but every motorcycle faces this problem after some miles. I faced the same problem with Suzuki.

    • Andrew says:

      From what I’ve seen, storage is what does it more than miles. I’ve seen the problem on a SilverWing 600 with under 5,000 miles, this VFR800 with under 8,000 miles, and a CBR (I forget which size) with probably 50,000 miles. All of them had been parked for at least a year without being run at all. On a related vein, I’ve seen fuel pumps ruined from improper storage. One actually still ran, unfortunately for its new owner, who got stuck with the repair bill two weeks after buying it used from a small dealer. The pile of rust we got out of that fuel tank was impressive.

  3. Andrew says:

    Just noticed this after peeking at our site’s traffic statistics: http://www.motohouston.com/forums/showpost.php?s=1a2c0c8321f28ffb6ac455090b138ceb&p=3624382&postcount=16

    Happy to read that this post helped someone else get their VFR running right again.

  4. Franklin says:

    You helped me out too. New FPR on order. Thanks for the write-up.

  5. Tomo says:

    You sir are a diamond….a long suffering VFR owner is now a happy chappy..

  6. John Wendel says:

    This is a genius insight. Two local shops were baffled by this problem. My 2003 VFR was in storage for over 3 years and exhibited this problem. This post, given to my mechanic was the solution. Just awesome to find this. You saved my bike!!! I am so grateful.

    • Andrew says:

      Glad it helped you! I recently came across a VTX1300 with the same problem. New owner bought it and it ran okay for a couple weeks, then… didn’t. Same exact problem with an external fuel pressure regulator that had gone bad due to long-term storage. Slightly different design than the one on the VFR, but much easier to access on the cruiser.

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