Need Help setting Float Level. 2nd Gen VFR750

Discussion in '1st & 2nd Generation 1983-1989' started by slowbird, Feb 20, 2011.

  1. invisible cities

    invisible cities New Member

    Country:
    United States
    Joined:
    Oct 20, 2009
    Messages:
    2,259
    Likes Received:
    2
    Trophy Points:
    36
    Location:
    new york
    Map
    Good deal.

    I am very much impressed with the patience you have shown in dialing in your carbs.

    It is great to see a fellow vintage Honda owner maintaining their own bike!
     
  2. slowbird

    slowbird Member

    Country:
    Canada
    Joined:
    Apr 18, 2008
    Messages:
    2,439
    Likes Received:
    0
    Trophy Points:
    51
    Location:
    Toronto, Ontario.
    Map
    Hahaha.....yeah. You have no idea the patience I am showing while I try and figure out this bike while my buddy (who now owns my old VF500) is riding around without any issues. :rolleyes:
     
  3. slowbird

    slowbird Member

    Country:
    Canada
    Joined:
    Apr 18, 2008
    Messages:
    2,439
    Likes Received:
    0
    Trophy Points:
    51
    Location:
    Toronto, Ontario.
    Map
    Update:

    Alright. It is about 6 C out (or 43 F )
    ...the pilots screws are 2 1/2 turns out. (1/4 turn out from where I started)

    Put the key in...No choke. Pressed the starter and it fired up for about 1 second before dying. Tried 2 more times....nothing.

    Choke to full. Pressed the starter and she fired up. Adjust the Choke lever a bit so she idled at about 2,500rpm. After about 30 seconds the idle started to go down and no matter where I put the choke lever the idle wanted to go down so I kept the idle steady with the throttle.

    Took her for a spin and it still feels fine. Once she's at temp she idles ok (just ok), and pulls nicely.

    IC....when I rev the bike...the revs come up smoothly. When I quickly roll off there is a split second where the idle hangs but it comes back down to idle nicely.

    I don't know if she's running a bit rich or a bit lean. :confused:

    With the outside temps as low as they are I'm thinking I should just double check the carb synch and leave it alone for now.
     
  4. invisible cities

    invisible cities New Member

    Country:
    United States
    Joined:
    Oct 20, 2009
    Messages:
    2,259
    Likes Received:
    2
    Trophy Points:
    36
    Location:
    new york
    Map
    If I could recommend, re-synch the carburetors with the engine fully warmed up (take for a short ride). After synchronizing take for another ride and see how the engine performs.
     
  5. slowbird

    slowbird Member

    Country:
    Canada
    Joined:
    Apr 18, 2008
    Messages:
    2,439
    Likes Received:
    0
    Trophy Points:
    51
    Location:
    Toronto, Ontario.
    Map
    LOL.....funny you say that cause that is exactly what I did after my last post. :tongue:

    So yea....Bike is at temp...set everything up and made sure my adjustments were made around the mark on the temp gauge where the bike usually operates at.

    The problem is I can't get a very accurate synch! :frown: I'll adjust the carbs so they are close to the Master carb but by the time I adjust the last carb the Master is at a different spot!

    Also....sometimes one of the bars on the carbtune would be fluttery and other times they would be smooth and stable.

    After adjusting the last carb the Carbtune would look like this:
    YouTube - V4 Carb Synch

    The idle was at the proper level...but when I'd give it some throttle the bars would match up and smoothen out. Something at Idle isn't right. :confused:

    Here is the closest I could get the carbs:
    YouTube - V4 Post Carb Synch

    (you can see in the 1st vid #1 and #3 have fluttery bars...and the 2nd vid only #1 does. I checked all connections and I do have the restrictors in the lines)
     
  6. slowbird

    slowbird Member

    Country:
    Canada
    Joined:
    Apr 18, 2008
    Messages:
    2,439
    Likes Received:
    0
    Trophy Points:
    51
    Location:
    Toronto, Ontario.
    Map
    Oh yeah....(almost forgot)

    I took the bike out after I synched the carbs again and the bike feels the same as before.
     
  7. invisible cities

    invisible cities New Member

    Country:
    United States
    Joined:
    Oct 20, 2009
    Messages:
    2,259
    Likes Received:
    2
    Trophy Points:
    36
    Location:
    new york
    Map
    I think you are pretty close here:

    [video=youtube;5aozKvaCB8U]http://www.youtube.com/watch?v=5aozKvaCB8U[/video]

    Is the engine performing better?
     
  8. slowbird

    slowbird Member

    Country:
    Canada
    Joined:
    Apr 18, 2008
    Messages:
    2,439
    Likes Received:
    0
    Trophy Points:
    51
    Location:
    Toronto, Ontario.
    Map

    I hope that's close cause that's the closest I can get it :tongue:

    I didn't notice any difference in the bikes performance....idle is the same. :confused:
     
  9. tinkerinWstuff

    tinkerinWstuff Administrator Staff Member

    Country:
    United States
    Joined:
    Oct 5, 2009
    Messages:
    7,831
    Likes Received:
    90
    Trophy Points:
    78
    Location:
    Colorado Front Range
    Map
    I would say it's plenty good enough. I'm puzzled why you appear to have more pulsating on the cylinder corresponding with the far left bar while the other three look to be quite smooth.

    Are there any vacuum lines T-d off on that cylinder operating a PAIR valve or carbon canister valve?

    Keep in mind that the sync only balances the amount of air (and hopefully fuel) being delivered to each cylinder. Do all cylinders respond similarly when f'n around with the air idle mixture screws? (the 2.5turns screws.....)
     
  10. slowbird

    slowbird Member

    Country:
    Canada
    Joined:
    Apr 18, 2008
    Messages:
    2,439
    Likes Received:
    0
    Trophy Points:
    51
    Location:
    Toronto, Ontario.
    Map
    Well you can see in the 1st video there are 2 fluctuating bars. The carb tune seems to have a mind of it's own.

    I dint recall seeing anything attached to that carb. ( it's the master carb )

    As the revs increase the idle smoothens out. Must be the idle screw settings???

    I have yet to play with the idle mixture screws while the bike is running...and I'm unsure of playing with them while it's still so cold out.

    They are currently at 2.5 turns out....I don't know if I should go in or out from here.
     
  11. tinkerinWstuff

    tinkerinWstuff Administrator Staff Member

    Country:
    United States
    Joined:
    Oct 5, 2009
    Messages:
    7,831
    Likes Received:
    90
    Trophy Points:
    78
    Location:
    Colorado Front Range
    Map
    and neither is anyone here. only the engine call tell you that. Adjusting while it warmed up and running will tell you that.
     
  12. slowbird

    slowbird Member

    Country:
    Canada
    Joined:
    Apr 18, 2008
    Messages:
    2,439
    Likes Received:
    0
    Trophy Points:
    51
    Location:
    Toronto, Ontario.
    Map
    Yea, I figured that. :redface:

    So I just follow what IC suggested?

    With the motor warm I turn one of the idle screws (on any carb in particular) outwards slowly until I hear the revs increase?

    Then turn the other screws out the same amount?
     
  13. invisible cities

    invisible cities New Member

    Country:
    United States
    Joined:
    Oct 20, 2009
    Messages:
    2,259
    Likes Received:
    2
    Trophy Points:
    36
    Location:
    new york
    Map
    With Keihin VD Series carbs (I believe that these are on your bike, but please double check) the pilot screws are typically positioned between 2 to 2-1/2 turns out.

    For reference this should give about a 3% CO reading on an EGA. An 80's era bike will often stumble or idle irregularly at 2% CO but will smooth out at 3% CO.

    Of course I understand that you don't have an EGA so this is why I suggested the 'tuning by ear' method as noted above. It takes patience but you are very close!
     
  14. tinkerinWstuff

    tinkerinWstuff Administrator Staff Member

    Country:
    United States
    Joined:
    Oct 5, 2009
    Messages:
    7,831
    Likes Received:
    90
    Trophy Points:
    78
    Location:
    Colorado Front Range
    Map
    2 to 2-1/2 turns is a factor of the pilot jet being the right size for the engine and altitude. For instance, if your bike decides it likes to be 3 or more turns out, you probably need a smaller pilot jet or the bike will run rich at 1/4 throttle.

    Not trying to confuse things, just attempting to point out that the screw adjustment is a factor of what pilot jet is installed and isn't a steadfast rule.
     
  15. invisible cities

    invisible cities New Member

    Country:
    United States
    Joined:
    Oct 20, 2009
    Messages:
    2,259
    Likes Received:
    2
    Trophy Points:
    36
    Location:
    new york
    Map
    Well noted, thanks.
     
  16. slowbird

    slowbird Member

    Country:
    Canada
    Joined:
    Apr 18, 2008
    Messages:
    2,439
    Likes Received:
    0
    Trophy Points:
    51
    Location:
    Toronto, Ontario.
    Map
    Alrighty....I'll start tinkering with the screws when it gets a tad warmer out.

    Thanks Gents.
     
  17. invisible cities

    invisible cities New Member

    Country:
    United States
    Joined:
    Oct 20, 2009
    Messages:
    2,259
    Likes Received:
    2
    Trophy Points:
    36
    Location:
    new york
    Map
    If I could recommend, stick with 1/4 turn increments. This is much easier to keep track of ;-)
     
  18. slowbird

    slowbird Member

    Country:
    Canada
    Joined:
    Apr 18, 2008
    Messages:
    2,439
    Likes Received:
    0
    Trophy Points:
    51
    Location:
    Toronto, Ontario.
    Map
    I will do just that. Thanks IC.
     
  19. squirrelman

    squirrelman Member

    Country:
    United States
    Joined:
    Jul 27, 2006
    Messages:
    9,838
    Likes Received:
    743
    Trophy Points:
    128
    Location:
    Buffalo, NY
    Map
    Mixture screws, pilot jets, small passages, cylinders can be slightly different, so what is optimum for one mixture screw would not necessarily be the best for another, and after proper tuning, it's likely that each screw would be custom-set, not all alike at some arbitrary # of turns.
     
  20. slowbird

    slowbird Member

    Country:
    Canada
    Joined:
    Apr 18, 2008
    Messages:
    2,439
    Likes Received:
    0
    Trophy Points:
    51
    Location:
    Toronto, Ontario.
    Map
    It was nicer out today.....took the bike for a long cruise. (80+km)

    Still runs funny in the idle-low rpm range. (goes like a rocket from there to redline)

    Tried turning the Pilot screws out slowly while the bike was running. I listened closely and couldn't hear any change in the idle...(if anything the idle started to sound worse)
    At about 1/2 turn out from where they were I stopped and put them back to where they were (+ 1/4 turn.)
    They are now probably at about 3 turns out I'd say.

    I assume it's running lean at idle....but only cause it gets better as the bike warms up.

    I don't know if the new Pilot Screws just suck or if I just need to keep fiddling with them.

    I'll wait for it to get a bit warmer I guess and see what I can figure out...I may try another 1/4 turn out and see if it fixes the issue....then maybe I gotta start screwing them in???
     
Related Topics

Share This Page