Engine vibration, high rpm.

Discussion in 'Mechanics Garage' started by DanBjR, Apr 1, 2020.

  1. DanBjR

    DanBjR New Member

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    Theres alot of threads on this but few if any came to resolution.

    I've got a high speed vibration, rpm dependent, felt in the pegs, seat, and bars. I notice this both under load at speed as well as in neutral standing still. Engine seems fairly smooth until aprox the point vtec kicks.

    I'm not sure if this is related but I also notice a tick, click, or knock in neutral at idle, especially when cold, that goes away when I pull the clutch. I had suspected the clutch basket but the sound is clearly on the left side. Unless im mistaken the clutch is on the right? Cct would be a guess but why would that stop with the clutch pulled?

    Lastly, I'm going to do a starter valve sync but I was told that only really effect low rpm operation so I'm unsure if its going to solve my issue.

    6th gen, 25k miles.
     
  2. GreginDenver

    GreginDenver New Member

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    Your post reminds me of one of my bikes, it's an older (2005 year model) Kawasaki EX250. The EX250 has a known tendency to have loose engine mount bolts, and the symptoms are very much like what you've described.

    On another topic: the engine running at idle and the transmission in neutral and the clutch not pulled in, means that the input shaft of the transmission is spinning but the output shaft is not spinning (however, because the gearbox is a "constant mesh" design several of the gears on the output shaft are spinning, with the VFR's 6 speed gearbox in neutral the cog pairs for 1st, 2nd, 3rd and 4th always rotate while the cog pairs for 5th and 6th are not driven but may rotate a bit due to oil-drag on the input shaft).

    This situation combined with the VFR's "lumpy" firing order (1-0-1-0-0-1-0-1-) means there's a good bit of gear-tooth banging going on inside the gearbox when the engine is idling. This is normally mostly muted by the engine oil. How old is your bike's engine oil? (Motorcycle gearboxes get noisier when the oil gets older)

    If you're noticing the "tick/click" at idle while the motorcycle is on its side stand it might be that due to the lean angle of the bike (induced by the side stand) it's allowing one end of the transmission to have less of the engine oil noise muting effect. Is this tick/click at idle the same when the bike is up on the center stand?
     
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  3. DanBjR

    DanBjR New Member

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    Thank you for the input. Oil is new, strait from honda. Oil level is at the full line, actually was a bit over that but I drained it back a touch. Has 300 miles or so since the change. Sound is present even when on the center stand as well.

    I'll double check the mounts tomorrow.
     
  4. DanBjR

    DanBjR New Member

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    Got into the bike yesterday, found the rear right starter valve was stuck open. Freed it up and adjusted all the best I could with a cm hg vac setup. Idle is much smoother eith only+/-50rpm surging now.

    2 things came up.

    1: I noticed there are two different size stacks in the airbox. I believe the taller ones had been in the front and shorter in rear however the diagram seems opposite. So I reinstalled with the taller in the rear. Can anyone answer definitively?

    2: the idle adjustment nob seems to have been turned so far as to locked up or possibly been broken. So I got that working but now my high idle is t working. As it looks like they are one unit, any thoughts?
     
  5. GreginDenver

    GreginDenver New Member

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    Maybe find a complete, used throttle body assembly (ebay?) and use it as a parts-donor?
     
  6. DanBjR

    DanBjR New Member

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    As far as I can tell the idle and high idle wax are one unit. I'm not sure exactly what is wrong. Idle adjuster was locked open and ever since I got it freed up the high idle is t working. Looks like theres a plate that the adjuster pushes on and possibly the same plate is actuated by the wax unit. I'm hoping it's just tweaked or stuck.
     
  7. tinkerinWstuff

    tinkerinWstuff Administrator Staff Member

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    Fuel tuning with a power commander smoothed out my high rpm vibration in the pegs.
     
  8. jacinda

    jacinda New Member

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    Nice[​IMG]
     
  9. DanBjR

    DanBjR New Member

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    Can anyone please confirm correct placement of the air intake stacks on the 6th gen? Do the taller pair go towards the front or back?
     
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