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RVF400 Cylinder drop

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by Rented, Jul 22, 2010.

  1. Guys, I really need some assistance with a problem I am having.

    I will try to describe the issue as accurately as possible.

    Whilst I am riding, the bike feels as if it is dropping a cylinder. This occurs when going over bumps (smaller high frequency bumps can do it), especially in turns. It will also do it when accelerating hard sometimes, especially in turns but also when standing up on smooth road as well.

    The exhaust note changes and the bike loses power.

    Due to my inexperience I am not totally sure if a cylinder is misfiring or perhaps fuel starvation is causing it?

    Whenever I take it to the mechanic I use (and he never charges me when he can't fix something, they're alright) it magically cures itself. They took it for three rides this week, and I go for a ride when they call me and it doesn't occur. A few days later it will do it again, quite badly.

    The bike has new plugs (God Damned expensive new plugs FFS), and I have checked the resistance on the ignition coils which is within spec.

    Any other ideas? I'm new to servicing bikes so I would really appreciate some help.

  2. My RVF400 had a very similar fault. Kept misfiring and yes hitting a bump in the road sometimes would cause it to start missing.
    I also noticed it was worse if it was very windy.
    Another strange fact with this fault was that when I investigated the fault by removing the tank and air filters to check the carbs, the fault seemed to be cured for a while, but would eventually come back.

    I was totally baffled by this weird problem but eventually found it.

    The main wiring loom has multiple connectors under the fuel tank just in front of the airfilter intake. To protect these connections there is a large rubber gaiter.
    This gaiter was being jarred by road bumps into the intake, also strong headwind must have caused a similar result.

    Make sure this gaiter is tied down, and cannot be moved into the air intake.
  3. An RVF in our family had a very similar problem too. It turned out a large connector in the wiring loom on the left side of the bike, with lots of wires in it (sorry I cant be more specific, it was a while ago) had corrosion on some of the pins. This was immediately evident upon opening the connecter and inpsecting the inside. Some pins were blackened/burnt. A new connector was soldered onto all the wires and the problem was fixed.
  4. Side stand switch.
  5. Side stand switch was also investigated on previous suggestions. Unfortunately it is not that easy.

    I know the loom down the left side of the bike. Looked OK. Checked connections all through the bike for corrosion.

    However, not the one near the airbox. Will check that, thanks.
  6. Check the earth connections, a bad earth could do it...

    Otherwise, I think you might have to through all the connectors & clean them up with some de-oxidiser. That would be a pain!