Need help

Discussion in '5th Generation 1998-2001' started by Goncalo, Jul 6, 2020.

  1. Goncalo

    Goncalo New Member

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    Dear friends,
    I have a 5th generation vfr, which since I owned, has issues, first issue:
    1)at low rpm, the bike seems jerky, unstable idle control(no fi errors), suddenly at 3k rpm, she kicks like she have turbo.
    2)issue, bike at cold seems OK, but as soon I get to traffic and gets hot and (very important), I get using several times the clucth, she gets jerky, hesitant, unstable idle, at low rpm (2k/3k) - in traffic-- trottle seems unresponsive - I really need help, I can figure it out. Best regards
     
  2. fink

    fink Member

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    All Hondas about that age on fi were a bit rubbish at very low revs, usual work round was use a different gear.

    Maybe your needing everything synced.
     
  3. Goncalo

    Goncalo New Member

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    I had synchro valves, replace tps, change spark plugs, change air filter... Well I don't know what to do more... I have 1992 vfr, is like silk, smooth, predictable in every situation, this one seems to have the famous gremlins....
     
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  4. Terry Smith

    Terry Smith Member

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    Idle issues are usually related to air leaks; maybe the throttle body rubbers, or a cracked or missing vacuum hose. Any sensor fault should be causing the FI light to come on. Another thing to check would be the fuel pressure regulator, take a look for liquid fuel in the vacuum hose to that, should be dry unless the diaphragm has ruptured. My 99 was easy and well mannered at low revs so something must be off with your one.
     
  5. Goncalo

    Goncalo New Member

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    I must confess if I wasn't a great fan of vfrs (I have 3, 1986 rc24 interceptor, 1992 rc36, and the wicked with 1999 rc46), my wife is always tell me to sell the crazy one, but I took personally, so, I must figure out, what's happening. I was wondering if I can share a video with you guys... Many thanks (I ll be in touch giving you guys news)
     
  6. GreginDenver

    GreginDenver New Member

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    The Honda PGM-FI ECU on the VFR800 uses two different methods to control fueling:

    Method #1: At small throttle opening (small Throttle Position Sensor "TPS" angles reported to the PGM-FI ECU) the controlling parameter for fueling is the Manifold Absolute Pressure "MAP" Sensor which is mounted on the rear corner of the bike's airbox and connected by a vacuum tube to the intake manifold.

    Method #2: From medium to wide-open throttle opening (large Throttle Position Sensor "TPS" angles reported to the PGM-FI ECU) the controlling parameter for fueling is the Throttle Position Sensor angle (a method known as "Alpha-N" in the fuel injection world).

    There is a very complete description of this in the Honda VFR800 Service Manual, Chapter 21, which is entitled: "Technical Features".

    The description that you have given of your problems makes me think there's something wrong with your bike's MAP sensor, or with its wiring to the ECU, or with its vacuum tubing connection to the intake manifold.
     
  7. Goncalo

    Goncalo New Member

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    The intriguing thing is at cold she seems OK, but as soon I start "messing" with clutch, in heavy traffic, she seems clogged, rough, even when the tempeture as become normal, seems more related with clutch than temperature. Can be R/R issues? I even thought that could be spark plug cables,... Someday after so many changes, I ll win this battle. With your help(for all of you guys)
     
  8. Terry Smith

    Terry Smith Member

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    Have you got a voltmeter fitted? That would at least enable you to see if battery voltage was an issue. I'm currently riding my 600cc Silverwing scooter with no charging system (dead alternator) and as long as I have a charged battery, it runs fine.

    What year is your VFR, do you have the manual fast idle lever or the wax unit?
     
  9. raYzerman

    raYzerman Member

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    While a few things can be involved, always good to start with the basics with electrical and vacuum connections, new plugs perhaps. However, I am going to suggest some reading for all Gen5 owners.... possible error in the FSM about Starter Valve Sync. I read this thread and re-adjusted my sync and it made a big improvement in idle and starting off from stops......
    https://www.vfrdiscussion.com/index...ct-for-22-years/&tab=comments#comment-1112093
     
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