Random loss in power/ stall

Discussion in '6th Generation 2002-2013' started by Robb, Oct 8, 2013.

  1. ZEN biker

    ZEN biker New Member

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    Power loss after extended down shifting is a evap issue. If you still have the evap system in place look for a vacuum leak or a disconnected purge solenoid.

    If you dont have a power commander, dont eliminate the o2 sensors. You can test this but mileage will suffer, the power commander programming fixes the mileage issue and tunes the performance issues some have found.

    This will sound stupid but a faulty map sensor or a vaccumm leak on the map sensor lines can also do this.
     
  2. Robb

    Robb New Member

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    Hi, thanks for your post. I'm fairly certian my bike does not have EVAP cannister. Where would I look for this? Also, what is the best way to check for VAC leaks, as I would like to do this with the lines on the throttle body as well. How can I test the MAP sensor and check those vac lines? Just pull them off and blow some compressed air through?

    No power commander here. I heard that some folks were having issues with a flatspot in the rev range, thought I would test this to see if it helps. I can always pull the resistors back out easily enought. Thanks for the tip on the mileage, hadn't thoguth of that
     
  3. ZEN biker

    ZEN biker New Member

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    I use ether and a straw from a wd-40 can, use very small squirts. Listen for the engine to speed up.

    Safer method as ether can cause issues that are very expensive is to use carb cleaner. Spray on a joint or tube and wait. The engine should bog down a little. Evap can is under the front of the engine. Purge solenoid is by the airbox, the flapper solenoid is up there too. The pair solenoid is behind the airbox by the map sensor. Carfully check for missing hoses and pinched tubing. The gas tank evap tube is under the tank and is easily pinched.
     
  4. nearfreezing

    nearfreezing New Member

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    If you need the shop manual, you can find it at vfrdiscussion under the downloads section.
     
  5. ZEN biker

    ZEN biker New Member

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    While your slummin get the honda common service manual.
     
  6. Robb

    Robb New Member

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    Thanks folks, I do have an E-copy of the shop manual on my computer.

    Last night I did the following:

    Pulled right side faring and cleaned all electrical connections I could find. I found 1 wire on a connection that looked a little on the burnt side. I cut the wire out and soldered the connection together. I sprayed some electrical cleaner in the MAP electrical connections. Have not had a chance to look for vac leaks, need to pick up a can of ether. Also re-cleaned the kill switch.

    I also disconnected the vent lines from the tank and blew some compressed air through, to knock out any crap that might have been in there and checked for pinches.

    Re-connected the battery and fired off the bike. I must say, I'm not sure it it's the placibo effect or what but the throttle responce seems much better. Have not had a chance to go for a ride (pouring rain) but even in neutral it seems much better. Think I'll leave the o2 sensor bypass in for now, monitor the mileage and see how it does. Will be able to go for a test ride tomorrow provided the weather lets up some.

    Thanks again
     
  7. VIFFER RIDER

    VIFFER RIDER New Member

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    I've had similar issues riding my newly acquired 02 viffer from Vegas, after tearing it down I discovered a fuel pressure regular diaphragm leaked and it as feeling extra fuel through the vacuum lines causing my bike to run like crap. Put the vacuum line off the fpr and look for traces of gas.
     
  8. whiskey9cjo

    whiskey9cjo New Member

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    Apologies for necroing this.

    I had this problem on a 2008 VFR800 with 28,000mi. After a long downshift, after about 30-45 minutes, it would occasionally drop a cylinder or lose power if I lingered in the 4-5k RPM range. Typically blipping the throttle would fix it and I could keep going down the road.

    I tried a few things that in hindsight seem pretty silly. I found this thread and began wondering if it was the evap system.

    Cold, the evap vacuum line going to the engine was difficult to remove from the purge solenoid..so I assumed there wouldn’t have been a vacuum leak there. I checked the electrical connection - it seemed fine.

    Just the other day it dropped a cylinder as I was pulling into my drive. I pulled on the vacuum line and it slid off, with almost no resistance. At this point I assumed that’s where the vacuum leak was, and it seemed to be temperature related. I pulled the vacuum line off and plugged it. It’s now been about a week and the problem hasn’t returned.

    I want to thank the person that suggested this might be an evap system problem. It pointed me in the right direction for a problem that has been plaguing me for some time.

    My next step will likely be to check the purge solenoid and possibly replace it and the vacuum hose.
     
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  9. Legnd

    Legnd New Member

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    This is great info, Whiskey.

    Can you describe or confirm my suspicions that I have the same issue as you?

    Bike starts and runs fine but on longer flat throttle if feels as though I'm running out of gas. Bucking is too harsh of a word but a little bit of hesitation or surging, but just slightly, enough to make me think my right hand has moved a tiny bit.

    If I pull up to a stop sign it may sound/feel like it's running a cylinder down and bog or even die. I can save it by throttling a bit. Bike starts right back up afterwards.
    Does this sound like your experience and can you circle or point out exactly what you pulled/blocked?
    upload_2019-11-8_20-5-18.png
    Or is it part of this diagram?
    upload_2019-11-8_20-9-7.png
     
  10. whiskey9cjo

    whiskey9cjo New Member

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    Hello legnd!!

    Apologies for taking so long to reply. I ended up plugging hose #5 on the second diagram. I’m not certain it was the right thing to do, but it *seems* to work. (Shrug)

    And yes, it seems similar to the problem you describe. I was able to predict when I needed to blip the throttle at the next stop based on how the throttle behaved while riding.


    Sent from my iPhone using Tapatalk
     
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  11. Legnd

    Legnd New Member

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    No worries Whiskey, appreciate the info.
    It's currently mid 20's ºF here so I probably won't be touching the bike for a little while.
    I'll play around with ziptie-ing the vac lines on this spring and see if it still happens. Thanks again!
     
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