Noise and power change at 6000 RPM in 6th gear?

Discussion in '6th Generation 2002-2013' started by Rome1, Aug 23, 2021.

  1. Rome1

    Rome1 New Member

    Country:
    United States
    Joined:
    Dec 21, 2007
    Messages:
    13
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    MOUNT VERNON WA
    Map
    My 2002 VFR 800 is making a strange surging type motor noise at 6,000 rpm in sixth gear. This is right around the 80 MPH point. I can only hear the surging noise when I am down behind the windshield. If I am in a normal sitting position it cannot be heard due to the wind noise. It sounds like a surging growling like it is having trouble continuing to accelerate. It also seems like a there is a small loss of power at this point as well although it will push its way past it as it revs higher and the noise disappears. The bike has 34,000 miles on it.
    I do not think it is related but my fan stuck on on the same trip and it does not turn off.
    Any thoughts on what might be the issue are appreciated.
     
  2. philois1984

    philois1984 New Member

    Country:
    Australia
    Joined:
    Jul 11, 2016
    Messages:
    118
    Likes Received:
    71
    Trophy Points:
    28
    Location:
    Queensland, Australia
    Map
    I would assume it is the VTEC cutting in, but there shouldn’t be a loss of power. On the 8th gen’s it cuts in around 6500RPM. No idea why it would struggle or hesitate to get past this point.
     
  3. Rome1

    Rome1 New Member

    Country:
    United States
    Joined:
    Dec 21, 2007
    Messages:
    13
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    MOUNT VERNON WA
    Map
    I have owned the bike for many years. This is different from the VTEC's normal turning on sound which is pleasing and growly. It seems like it is struggling to move up in RPM's for some reason. It is quite noticeable when I am down behind the screen.
     
  4. Viffer J

    Viffer J New Member

    Country:
    United States
    Joined:
    Jun 30, 2017
    Messages:
    160
    Likes Received:
    85
    Trophy Points:
    28
    Location:
    PNW
    Fuel pressure regulator maybe? :Noidea:
     
  5. Terry Smith

    Terry Smith Member

    Country:
    Kuwait
    Joined:
    Nov 18, 2013
    Messages:
    2,727
    Likes Received:
    625
    Trophy Points:
    128
    Location:
    Auckland, New Zealand
    Map
    I know the VTEC sppol valve operation is dependent on the coolant temperature being beyond a minimum point; does this tie into the fan running behaviour at all. Maybe the temperature sending unit (or wiring) is faulty? How does the dash temperature readout look?
     
  6. Diving Pete

    Diving Pete Member

    Country:
    United Kingdom
    Joined:
    Mar 25, 2016
    Messages:
    1,969
    Likes Received:
    548
    Trophy Points:
    143
    Location:
    London
    Map
    When was the last time the valves were checked?

    At the point of VTEC, - roughly 6000rpm you will get a small dip in torque - especially if you are sitting on the transition point. This is due to more valves opening but no more fuel. Essentially don't sit on the transition.
     
  7. skimad4x4

    skimad4x4 "Official" VFRWorld Greeter

    Country:
    France
    Joined:
    Jul 5, 2009
    Messages:
    2,269
    Likes Received:
    369
    Trophy Points:
    113
    Location:
    French Alps & London
    Map
    It is rare for a vehicle to develop more than one fault simultaneously - problems tend to be linked.

    If the ECU thinks the bike is still cold then VTEC is inhibited so that might explain the unusual noise. The ECU looks at the water temperature sensor output - so perhaps adjust the display to show coolant temperature and then take the bike for a ride - if it stays low - that problem needs to be resolved first (possibly coolant level sitting below the sensor or a jammed open thermostat) and may eliminate the surging noise.

    However if your bike is heating up correctly does this noise only happen at 6,000 rpm in 6th Gear? Or does it happen at around 6,000 RPM in 5th or 4th? Does the noise stop/reduce when you pull in the clutch and coast?

    If it only happens in 6th then it sounds like its the power train - so clutch, gearbox, sprockets and chain state and tension...

    If the noise occurs at 6,000 RPM in other gears then it could be your fuel pump/pressure regulator is failing or a valve check/adjustment may be needed to sort things out.

    Good luck let us know how you get on.

    SkiMad
     
  8. Rome1

    Rome1 New Member

    Country:
    United States
    Joined:
    Dec 21, 2007
    Messages:
    13
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    MOUNT VERNON WA
    Map
    I believe the valves were checked at 20,000 and were in spec but I will need to check my records to confirm the mileage. The heat gauge seems to be operating fine and I did notice it around 180 on at least one occasion. I did not notice the noise when I dropped it to 5th gear but I will give it a ride this week and follow back up with what I have found out related to the questions. Thanks again for the ideas and feedback.
     
Related Topics

Share This Page