1990 vfr vibrating?! Help!

Discussion in 'Mechanics Garage' started by 750, Aug 30, 2014.

  1. 750

    750 New Member

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    Hi all

    after cleaning my carbs and making sure everything was back on properly, my bike ran well for a day - when I returned to it, turning the bike over the exhaust sounds a bit louder and the bike vibrates in neutral at a stand still, the power feels none existent as well when I set off :(

    Also on a side note, can I fit a 94-97 exhaust straight on as I want to get rid of the collector box to save weight.

    Thanks for any replies!
     
  2. VFRnewbie

    VFRnewbie New Member

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    Were the carbs completely disassembled into their compenent parts, or did you leave the jets etc in place? Is the idle speed the same as before once the bike's warmed up?

    It can sure be disheartening when something works less well after you've spent a loada time working on it, but don't let it getcha down, it's probably an easy fix, just a case of something not quite back where it should be...
     
  3. ridervfr

    ridervfr Member

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    You gota remove them again and go through the "drill" again. Side bar: you could spray some carb cleaner near the rubber plenums and see if the idle fluctuates, if it does, then you have an air leak. You could have pinched a diaphram or two too, jury is oot though.

    If I were you, I would replace these as good measure, they are still available. Gen 4 will work, but you have to replace the entire exhaust system.
     
  4. 750

    750 New Member

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    Got a good place to get the diaphragms? Mine are in good shape I think! One was a bit fussy trying to get it lined up properly but the suction seemed good enough on all of 'em. Very disheartening.

    Good to know about the exhaust, I'm umming and ahhing about getting a left side exit one...
     
  5. squirrelman

    squirrelman Member

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    Since you had the petrol tank off, one or both of the 2 rubber tank "buffers" could have fallen off, leaving you with a tank that vibrates alot.

    Another guess: vibration along with low power suggests that one or more cylinders are not firing proppaly.:crushed:
     
  6. 750

    750 New Member

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    Was wondering if the cylinders might be off, any sure fire way to tell?
     
  7. ridervfr

    ridervfr Member

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    Spray some WD-40 on each header pipe closest to the head? You could use a lazer thermometer too on the headers?
     
  8. ridervfr

    ridervfr Member

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    Could buy a Thexton spark tester too, may have to modify it though to work on our type of spark plugs. Its carburation dollars to donuts :homer:
     
  9. 750

    750 New Member

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    Well I've bought a carbtune to keep for future use so will try that first off and ensure the robber tank mounts are in place. Will stick an update up soon.
     
  10. 750

    750 New Member

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  11. ridervfr

    ridervfr Member

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    You have to do the "drill" again, that means, remove from bike and take your carb hats off or what ever you call them. You should see them rising, your not, so your screwed. You may have pinched something when you were tightening those screws or you may have perished diaphrams. I tend to dought the ripped diaphram thing.

    When you take the carbs off the bike and are satisfied that you did'nt pinch one or more of those diaphrams, the way to test it before you re-mount them, is to BLOW air into the T-FITTING thats at the base of the carbs, (as the carbs sit on the bike, its towards the rear.) When your blowing, you should be able to see those slide RISE> if not do the "drill" again. Let us know, I had compromised finger fucked carbs and ended up getting a donor set from Ebay. You may be ok though, I don't think you "guys" have the type of monkeys we have here in the states. ie; little knowledge and a basic set of spanners which they confuse with being able to properly "turn a spanner with care." :loco: btw, had my junkyard dawg up to 140 mph for a few ticks and cruised at 120 for miles :vtr2: Good Luck
     
  12. 750

    750 New Member

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    I think the diaphragm's are junk. The rubbers looked a bit wrinkly, might just buy some more carbs as they're cheaper than buying new diaphragm's.
     
  13. kennybobby

    kennybobby New Member

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    It looks like you found the culprit--Carb #4 slide was not moving (front right).
     
  14. ridervfr

    ridervfr Member

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    It should be a symphony of four slides rising in uinson. Pretty music really, kinda like skeltons rattling around.
     
  15. 750

    750 New Member

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    Shouldn't all four move much more when giving it a fist full of revs like I was? I assumed the moved all the way up rather than fluttering like they are at the moment.
     
  16. ridervfr

    ridervfr Member

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    Yeh, they should move almost all the way up.
     
  17. kennybobby

    kennybobby New Member

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    Depends upon RPM and airflow--blipping the throttle won't do it, have to hold some high revs and airflow to see them lift...
     
  18. ridervfr

    ridervfr Member

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    I have to disagree, if you take the tank off and the top part of the air box and start and run the bike with a nurse bottle, those slides should move more than their moving, (end of story.) I had a similar situation with my latest gen 3. If you take those carbs off the bike and blow air thru the t-fitting like we were discussing above, you should get decent movement, bear in mind, this is compressed air. On the bike like your videoing, those slides should be rising without having to rev the snot oot of your :scooter: Gool Luck and keep us ah-breast of the situation :loco:
     
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