Carb issues or something else? (R90/6)

Discussion in 'Airheads' started by lmyamen, Apr 16, 2012.

  1. lmyamen

    lmyamen Been here awhile

    Joined:
    Nov 29, 2011
    Oddometer:
    555
    Location:
    Des Moines, IA
    Hey guys/gals thought I would ask here. I am noticing a problem when accelerating on the interstate. When traveling at 60-65mph and I accelerate it starts out fine but then it kind of cuts out almost like a feeling of the gas being restricted and not flowing. It does not show any symptoms of this at lower speeds under 50mph when traveling through town and the clutch is definitely not slipping when I am accelerating. I am wondering if this could be caused by dirt carbs? I was talking with my father and he said maybe something has gotten into the carburetors after having the tank off and doing all the paint work. Going to take a further look at it tonight though, any other options of what could be causing the hesitation?


    my bike

    [​IMG]
    #1
  2. robsmoto

    robsmoto Motorcycleton

    Joined:
    Jul 15, 2001
    Oddometer:
    338
    Location:
    Columbus, Ohio
    check the vent for the tank (in fuel cap,I've used B-12 to clean, replace cork or rubber gasket afterwards)
    check the in-line fuel filter, if present - replace or clean
    drain gas from tank, remove petcock, check screen and tube for crud - clean and/or replace
    check diaphrams at carb tops, if torn will give poor top end performance, replace if needed
    remove bottom bowl from carb, check for water, crud, gas varnish. If necessary remove jets, clean with B-12, replace o-rings (I find it easier to just remove carbs at this point for a proper cleaning).
    #2
  3. supershaft

    supershaft because I can

    Joined:
    Sep 9, 2010
    Oddometer:
    9,116
    Location:
    San Francisco Bay area
    It could be about anything but the first thing I would do is pull the floats and look very carefully for water in your bowl. If the water is clean, it is very hard to see. Then check and make sure you floats are adjusting right and the fuel shut off is working. First things first! No need to tear it apart just yet. Good luck!
    #3
  4. chasbmw

    chasbmw Long timer

    Joined:
    Feb 19, 2006
    Oddometer:
    2,702
    Location:
    Bath Uk
    My betting is that the float height is set too low, unlikely to be diaphragms at this speed.

    Cheap and easy cure
    #4
  5. lmyamen

    lmyamen Been here awhile

    Joined:
    Nov 29, 2011
    Oddometer:
    555
    Location:
    Des Moines, IA
    We will find out more when I take the interstate this evening, but last night opened up the carbs and one of them had some debris of some sort in the float bowl, cleaned it out and seems to be running great. Took it for a quick ride on the interstate last night afterward and no signs of missing.
    #5
  6. cycleman2

    cycleman2 Been here awhile

    Joined:
    Jan 18, 2010
    Oddometer:
    617
    Location:
    Alberta, Canada
    Put a dose of Sea Foam into the tank. It really helps to clean out the carb orfices and is a good treatment to use once and a while.
    #6
  7. sigpe57

    sigpe57 Been here awhile

    Joined:
    Oct 11, 2005
    Oddometer:
    349
    The fuel-cut-out happened to several of my BMWs. One bike it cut out at 70mph or higher. One bike cut out at 10mph. It's all caused by weak rubber diaphram. I replaced the diaphram. The cut-out problem goes away.

    TT
    #7
  8. Boxer Metal

    Boxer Metal Mad Scientist

    Joined:
    Nov 3, 2003
    Oddometer:
    3,609
    Location:
    Chico, California
    I agree. Make sure your points and condenser are good and your getting full advance.
    #8