Throttle sync by ear

Discussion in 'GS Boxers' started by mysticbus, Nov 18, 2013.

  1. mysticbus

    mysticbus Mysticbus

    Mar 17, 2010
    Daytona Beach, FL
    So last week I pulled both of those brass plugs out of my throttle bodies, they were dirty, I cleaned them, and cleaned the holes too. Put em back in and turned em out 1 turn each, idle was a tad low, I ended up going 1.5 turns each to get a hair above 1KRPM.
    I also noticed the vibration had been pretty noticeable above 4K RPM, so I then cracked the right side cable lock nut loose, and adjusted by "ear" and "feel" at 3KRPMs, I got it where it was really smooth sounding and tightened it up.
    Rode it around and it felt REALLY good and smooth. But, I ordered a carb mate just to do it right.
    It came today. I put it on after warming the bike up, and at the lowest sensitivity, it showed green light at idle, I swung the dial to the most sensitive, and it went to a blinking amber light 1 position off center, so a quick little nudge on the right side brass plug got it right on the money at the highest sensitivity.
    I left it at that sensitivity and wound the bike up to 3KRPMs, and umm... it was dead on.
    what can I say? Is setting it by ear/feel a viable method?
    On another note, after the first adjust by ear, it was super smooth well into the 5-6K range, and where it felt buzzy at 4K it now feels like an electric motor it is so smooth.
  2. markjenn

    markjenn Long timer

    Nov 9, 2003
    Bellingham, WA
    If you have a good feel for these things, it probably can get things reasonably close. But even after you managed to get a good setting without the instrument, using the instrument improved things, so I don't think "ballparking it" by feel is a good substitute for having the right tools.

    On old Honda twins (with no taps in the intake parts), the owner's manual recommended carbs be balanced at idle, but putting your hands at the exhaust outlets and adjusting for equal exhaust pulse pressure. That seemed pretty lame to me. Another shadetree technique was to bump idle enough that the engine would still run on only one cylinder, then short out each side, adjusting the idle screws to get equal RPM drops. Then back down both idle screws equally. For balancing when the butterflys were off the idle stops, you'd reach into the intake throats with two fingers on one hand and adjust the throttle cable so that the butterflys just came off their idle stops at exactly the same time.

    Lots of shadetree stuff out there which works pretty well, but the proper tools work better.

    - Mark
  3. Steptoe

    Steptoe steptoe

    Feb 21, 2004
    london, England
    I do airheads by ear, have done for the last 20 years.

    On the 1100/1150 models I can get the idle spot on by ear, but under load i can't get them as close as by ear as i can using the harmonizer.

    But then again, most of the other balancers available can't get it as close as the harmonizer. :D
  4. roger 04 rt

    roger 04 rt Long timer

    Nov 9, 2011
    Another very good Oilhead tuner I know uses gauges to get idle and something like 3K right. Then he rides with the right side adjuster from 1/4 counterclockwise to 1/4 clockwise and chooses the final setting bases on vibration at a couple rpms, on the road, under load.
  5. jdub

    jdub Dawg bytes reel gud

    Jan 7, 2004
    S. Central PA
    Exactly what I've learned to do on my GSA, except I do the final roadside fine tune adjustment on the left side. Even when my Carb-Stix indicates the TB balance is dead-on, I fine tune out any residual vibes in this manner.