High RPM

Discussion in 'Airheads' started by gvganser, Apr 1, 2013.

  1. mark1305

    mark1305 Old Enough To Know Better

    Joined:
    Feb 7, 2005
    Oddometer:
    6,318
    Location:
    Merritt Island, FL
    As per 109e's comments.... The idle stop screws are the first and simplest place to start while synching and fine tuning the carbs. I have had high and hanging idle before when everything was in good shape but the idle stops were set just a fraction too high. More than once. (I try to keep my idle at about 1000 rpm for better cam oiling at idle.)

    +1 on at least a 10 mile warmup - more if you are in cold temps.
    #21
  2. Plaka

    Plaka Brevis illi vita est

    Joined:
    Jun 19, 2010
    Oddometer:
    4,625
    Actually your start your tune with the idle mixture. if that is off it affects the mixture well into the needle jet range. having that off and trying to make up for it with the idle stop screws is a mistake.
    #22
  3. gvganser

    gvganser Adventurer

    Joined:
    Aug 28, 2010
    Oddometer:
    44
    Location:
    Maryland
    Ok. So the idle stop was definitely the main ingredient to the secret sauce. Turned those back and what a difference it made. I still have to finish the sync. I understand the concepts here and the info you have given has helped with that.... My execution seems to be piss poor even though I thought I had proper preparation.

    There is a MD airhead tech barn in a couple weeks. My goal was going to be just go and meet some of the Airheads I hadn't met before but I think I will see if I can have somebody walk me through... I'm having a hard listening and finding sweet spots.

    Thanks again for all of your advice ad information.
    #23
  4. brittrunyon

    brittrunyon R 100 GS F 650 GS

    Joined:
    Oct 6, 2010
    Oddometer:
    645
    Location:
    The High Desert of New Mexico
    Found this..................
    I wonder what the experts say about it :ear

    [​IMG]
    #24
  5. Plaka

    Plaka Brevis illi vita est

    Joined:
    Jun 19, 2010
    Oddometer:
    4,625
    Somebody got it completely screwed up.

    Sigh, it's so simple but seems so out of reach for too many...
    #25
  6. brittrunyon

    brittrunyon R 100 GS F 650 GS

    Joined:
    Oct 6, 2010
    Oddometer:
    645
    Location:
    The High Desert of New Mexico

    Okie Dokie, sorry for posting that :eek1 , not sure where I found it.......:scratch

    No worries, I'll toss it out for the dogs.

    But now I'm for sure taking notes.
    #26
  7. Plaka

    Plaka Brevis illi vita est

    Joined:
    Jun 19, 2010
    Oddometer:
    4,625
    You could keep some of it, unscramble some of it and correct the numbers for some of it.

    I've written this up from memory a couple times. I suppose when I have a min I'll do a page on it. I still have my quickly scribbled notes from when I was taught to do it a whole lot of years ago.


    If somebody in the longmont/ boulder/denver area has video gear we could film it.
    #27
  8. disston

    disston ShadeTreeExpert

    Joined:
    Mar 22, 2011
    Oddometer:
    12,368
    Location:
    Silver Spring, Md
    I don't see what Plaka's problem is with the balancing method presented. That is basically how I do it. What am I doing wrong?

    I will admit that my carbs will not maintain a nice idle. I have to blip the throttle to keep the engine rpms out of the basement. But if I set them up any I end up with a 1500 rpm idle.
    #28
  9. Plaka

    Plaka Brevis illi vita est

    Joined:
    Jun 19, 2010
    Oddometer:
    4,625
    I'll get to that. Do it right and the idle is no problem.

    You set idle mixture first, idle speed second, cruising rpm third and go back and touch up the idle speed again last---usually on your test ride.

    This one gets step 1 and 2 backwards and misses the cruising RPM and final idle speed altogether. And while you will get it by ear quickly enough, you do look at the tach (provided it works). You have the cables max slack for idle and very slight slack only for the high rpm balance. You ensure the chokes are closed at all times.

    It does pick up the slip of paper trick. I'm getting tired of that and I'll dedicate a feeler gauge I never use and count turns to zero the screw.

    I've done this so many times since I learned it it isn't funny (50+?). It comes out really well every time.

    My latest setup will short all four plugs which will be new. I used to do my dual plug engines with the bottom plugs shorted and left that way. My toolkit sticks still work that way. The new sticks kill all four.

    I was making a rig to short through plugs for the last Nth...blew it off.
    #29
  10. lkchris

    lkchris Albuquerque

    Joined:
    Feb 23, 2005
    Oddometer:
    1,097
    There has to be slack in the throttle cables. This can go away with heat.

    I had an Airhead once that idled at 2K rpm and the cause was no compression in one cylinder.
    #30
  11. Plaka

    Plaka Brevis illi vita est

    Joined:
    Jun 19, 2010
    Oddometer:
    4,625
    Here ya go:

    http://www.eskimo.com/~newowl/setting_airhead_CV_carbs.html
    #31
  12. Plaka

    Plaka Brevis illi vita est

    Joined:
    Jun 19, 2010
    Oddometer:
    4,625
    Sticky advance weights will do that to.

    When you vacuum balance you can get both sides to pull the same vacuum even with bad compression on one side. If you power balance it'll just never happen.
    #32