6500rpm power dip or slipping clutch?

Discussion in 'Mechanics Garage' started by DanBjR, Mar 26, 2020.

  1. DanBjR

    DanBjR New Member

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    Noticed a "dip" in power around 6-7k right as you feel the vtech power band. Seemed to be after a little riding as I didnt notice it this morning. Last night after an hour of spirited riding I noticed it accelerating in 2nd and 3rd. Almost like the engine power dies for just a split second or a slipping clutch.

    But I didn't notice any clutch slip otherwise, mind you I'm not hard launching from a stop. Not sure if this is just normal or something easy? My clutch has zero freeplay and catches at the near end of the release, barely have to pull the lever to shift smoothly. 25k miles on the bike. 6th gen. Honda w40 oil, 200 miles since oil change.

    I've read the clutch plates are rather stout but I've also read the springs are on the weak side.

    Edit: to be clear, I do not "hear" any discernible engine cut out, though mostly just hear wind anyway. I guess I'll have to keep an eye on the tach to see if I notice rev spike.
     
  2. mofo

    mofo New Member

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    I guess the best you can do is keep an eye on the tachometer to make sure it is indeed a power dip to start isolating the issue.
     
  3. NorcalBoy

    NorcalBoy Member

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    How long have you owned the machine? If you haven't had it for very long, my first guess would be that you are experiencing the VTEC engagement dip, common with this engine in stock tune.
     
  4. DanBjR

    DanBjR New Member

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    Only had the bike a few weeks. I'm admittedly anal retentive on little things but I'm not sure If its normal behavior or something more.

    Did notice the bike feels flat just before and into the powerband if that makes sense but really noticed this in more gental acceleration..

    Today I paid more attention and heres what I noticed:

    Power loss is closer to 5k
    Tach doesn't noticeably hesitate or drop
    200rpm surging without load on the engine at all rpm ranges
    6k and up I've got a noticable high speed vibration(felt in the tank and peg areas but also the bars.
    Possibly have a slight misfire on one cylinder but not a dead or hard miss.
    High idle at cold startup seems intermittent? (40° weather and hours between starts.)


    I'm planning new plugs and possibly having the dealer do a starter valve sync. Any other thoughts?
     
  5. Allyance

    Allyance Insider

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    I had a 2003 for awhile, a Power Commander 111 took care roughness below 3k and any dips
     
  6. DanBjR

    DanBjR New Member

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    Power commander and exhaust along with the pair flapper and evap delete are in the future but I want to sort out anything and everything first so i have a baseline.
     
  7. DanBjR

    DanBjR New Member

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    Found this today, hopefully this resolves some of the power issues up top but no change to the rpm fluctuations.

    Also noticed a bit of gas/oil in the airbox.
     

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  8. Terry Smith

    Terry Smith Member

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    Were you laying in supplies in case of a lockdown???

    Have seen plenty of this from folks who have to lay up their bike for winter. Have also seen exhausts filled with similar mouse fodder.

    A bit of oil in the airbox is normal; there's a crankcase breather that discharges a bit of oil mist into the airbox, which then gets ingested by the engine or deposits on the walls. Overfilling with oil will make this very noticeable, but a trace is to be expected in any case.
     
  9. DanBjR

    DanBjR New Member

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    So some updates; replaced the spargplugs with honda oem NGK and after cleaning the filter, waiting on a replacement, the bike has alot more power across the whole rpm. Still not quite right yet tho. But progress
     
  10. GreginDenver

    GreginDenver New Member

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    pretty certain that Honda would have tested the engine extensively to determine the RPM at which the awesome VFR800VTEC V4 engine would "run out of breath" while running on 2 valves per cylinder. Then, after finding this RPM value, they would naturally place the RPM point where the VTEC kicks in (Yo!) so that the engine switches to 4-valve operation before reaching that 2-valve-per-cylinder "runs out of breath" point.

    Unfortunately, anything that makes the engine less volumetrically efficient, such as a mouse nest in the airbox, a mouse food-cache in the exhaust, or goofy "mods" like removing the airbox flapper, can/will have the effect of changing the point in the RPM range where the 2-valve-per-cylinder operation would "run out of breath". Possibly moving that point to somewhere below the programmed VTEC changeover.
     
  11. DanBjR

    DanBjR New Member

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    Its definitely been better since cleaning out the crap but I still noticed a little bit of it today. All else seems intact and unmolested in terms of modifications. I do also have a difficulty holding steady rpm/speed in the 5k range, it's not smooth or steady. Not that it's very bad but you can feel it either lurching I small bit or loosing a small amount of power. Its cyclical. I'm going to look at the chain to ensure it's not just a bad link I'm feeling.
     
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