R100/7 High Idle after long warm up

Discussion in 'Airheads' started by Highwood, Apr 9, 2013.

  1. Highwood

    Highwood Been here awhile

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    Yes, I do know what you mean. It DOES NOT sound like a V twin. The ghosting at idle is less than a 1/4". There is no ghosting at full advance.

    From Duane A. "How much error is too much? That is up to you. We found little, if any, improvement if the two marks are brought together from only 1/4" apart. .... The final indicator is the "F" mark. If it is good and the "S" is a bit out, forget about it. It is one of those things in life. "

    Sounds like I have "one of those things in life." I am too brutal with a hammer, and frankly too afraid, to try the fix idle ghost. I will take the advice of forgetting about it, particularly given the close proximity of the ghost (less than a 1/4" (maybe 1/8) and both s marks well within the window).

    Thanks for the link and advice.
    #21
  2. disston

    disston ShadeTreeExpert

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    I think that is the right decision given that the ghost is gone by the time of full advance. Full advance is much more important than idle.

    The procedure is scary. I had those feeling also but having done it I am more confident.

    I think it may go away completely with the new points.
    #22
  3. supershaft

    supershaft because I can

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    To fix the fast idle all you need to do is adjust your idle screw and mixture screw when the engine is good and hot. After you do that, it won't idle like it was when it is cold but who rides around with a could engine?
    #23
  4. Les_Garten

    Les_Garten Been here awhile

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    First things I would confirm:

    When it is doing the behavior

    1) Push on the linkages on the carbs for the butterflies and chokes and make SURE they are in idle and off positions. This is the very first thing that absolutely has to be put to bed. You want to know if your carb shafts or linkages or cables are out of whack or not.

    2) I've never used WD-40 to check for vacuum leaks, but it doesn't impress me much from the sound of it. One thing that will work well if you have one is a Torch with a pencil type tip with Map Gas. This is really nice because you can regulate flow, turn it off and on and very finely direct the flow. I have one like the one below and it is really handy for this.

    [​IMG]

    3) CONFIRM there are no vacuum leaks especially around the spigots.

    4) If you have a timing light, check the timing if you think it is sticking in some strange fashion. A programmable timing light would be the shiznit here.

    Here is the one I use(very handy):
    [​IMG]


    Now quit goofin' around and figure this bad boy out and don't leave us hangin'!
    #24
  5. hardwaregrrl

    hardwaregrrl ignore list

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    If you are going to evaluate your plugs by using the "chop" method, get some ethanol free gas. Usually can find it at gas stations near a lake and a set of new plugs.

    plug chop
    #25
  6. supershaft

    supershaft because I can

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    IMO, 99% of everybody has no business doing plug chops. If they can afford all the plugs to do anything close to real comparisons, most everybody still thinks too rich is too lean. IMO, forget it. Go by how it runs and the piston crown IF you are really tuning it for best power. Anywhere close to best power and new plugs will be mostly all white.

    Vacuum leak? That's usually at the carb spigots that have already been mentioned but what about the enricher body gasket? That's the other most likely source.

    The OP needs to get some points and adjust his timing but the fast idle is most always simply about adjusting the idle AFTER the engine is FULLY warmed up. His description of how it idles cold tells me with some certainty that he has not done that.
    #26
  7. ME 109

    ME 109 Long timer

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    Is that likely given a idle rpm of up to 3000?

    and what of the idle returning to normal after turning off, and restarting?
    #27
  8. Highwood

    Highwood Been here awhile

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    Thanks for the link to a description of "plug chopping." I'll give that some thought. There's lots of wide open prairie to the east.

    Before I do anything else, I need to get properly-gapped, non-pitted points, a good condenser and the timing set. Then I'll go for a proper run and see if I can recreate the problem.

    I have a suspicion that it is a multi-issue problem (points, timing, atu, idle screw, mixture screw), therefore requiring a disciplined approach. If I change too many things at once, I won't know what made a difference. I do believe the key is a very full warm up. I suspect I'll be riding around with a screwdriver and a manometer for a while.

    Off for four days with my sweetie. Points and condensor won't be in until late next week earliest. Those that are helping deserve, at the very minimum, to know how it turns out. I promise to report back post points and timing.
    #28
  9. supershaft

    supershaft because I can

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    Carb adjustment, carb adjustment, and carb adjustment.
    #29
  10. photorider

    photorider Been here awhile

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    I can't remember if this has been brought up but are your throttle cables in good shape?
    I've seen throttle cables ruined by being careless when removing the carbs. This can also cause the idle to "hang."

    Did the throttle shaft o-ring get replaced when you rebuilt the carbs (often they are not)? They can also cause a condition similar to what you describe.

    Good luck with the diagnosing and let us know what you find.
    #30
  11. Plaka

    Plaka Brevis illi vita est

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    Pitting on the points won't matter, you file off the tit so you can get a feeler gauge in there to gap them. But once they get pitted it keeps up and your dwell settings won't hold. So you replace them. But I used to keep a points file in my toolkit anyway.
    #31
  12. Plaka

    Plaka Brevis illi vita est

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    I know nothing about the Omega.

    I was not happy with two Dyna units in a row. When they failed, as all electronics do eventually, they went intermittent, which was difficult to diagnose. Talking with the people at Dyna was not pleasant.

    I got a Boyer and liked it. It died eventually, dead as in dead, easy to diagnose and lasted long enough for me to be very satisfied I got my moneys worth. I bought another and it was still going strong when I parted out the bike years later.
    #32
  13. ME 109

    ME 109 Long timer

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    Man I've been looking all over my bike for that third carb. Danged if I can find it. :huh
    Where the hell is it?
    #33
  14. Highwood

    Highwood Been here awhile

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    So, got the new points and condenser. After a short swearing session getting the points gapped correctly, including sacrificing a .38mm feeler gauge to a length I could work with, I fired the bike up and it ran like shit.

    Got out my timing light and it was running well advanced and almost 1500rpm at idle. More swearing and I got the bike timed well at idle and very well at full advance, though the idle settings were still too high. (Seems remarkable to me that the timing was so advanced given i did not adjust the timing to install the new points.)

    Set about adjusting idle mixture and idle stops and noticed the left carb wasn't responding as well as the right carb. Since I had all the settings ballled up anyway, I decided to check the needle settings. Off with the top of the the carbs and the discovery that the needles were at the highest setting, not the third notch as indicated by snowbum et al. Adjusted the needles and reinstalled.

    Cleaned and gapped the plugs, garage set the mixture and idle to 1050 rpm including balance at idle and just off idle with homemade manometer (20ft of 1/4 inch hose and 15 inches per side of two-stroke oil). Took the bike out for a short blast, including some runs up a steep hill in 4th gear, accelerating from 2500rpm to redline.

    Bike is running well now, but is was 3C and late in the day and I only rode it for about 30 minutes. I haven't had a chance to run it for a half hour or more at a cruise. That being said, it started beautifully from cold (6C in garage) with full choke and idle at 850ish. Plugs are a proper tan colour indicating that mixture is at least close to correct. Bike returned to proper idle throughout the test run.

    I think I may have it sorted.

    It was -10 this morning, but the sun is out. Perhaps I can get it out this afternoon for a proper, extended run and I'll confirm all is right with the world.

    Thank you to all for your kind help.
    #34
    Ben Muck likes this.
  15. swanker

    swanker Shadetree Tinkerer

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    :clap
    Hell yeah, a big +1 to that!
    Great job there and something for me to keep in mind as I troubleshoot my high idle issue.
    :clap
    #35
  16. Plaka

    Plaka Brevis illi vita est

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    Now I'd get a points file. it doesn't fix the points, it just gets the little tit off so you can get an accurate setting. Goes in the on-bike toolkit for roadside repairs. Some dirt in the points compartment can hurt those point faces and on a trip, it's nice to be able to dress them and reset and just keep going.

    If you know a diabetic score some alcohol pads off them. Real handy for cleaning points (and halogen bulbs). Not good for glasses. But they keep well. You could buy a box too but it's a multi lifetime supply.
    #36
  17. Highwood

    Highwood Been here awhile

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    Weather got to 8C and that was good enough for me.
    Took a 30 minute ride throughout the rpm range, even breaking a few laws with pulls up over 140kph..
    Took a screw driver and did a final tweak on mixture on the side of the road. Returned to garage and rebalanced everything with manometer, then back out for another run.
    Smooth, smooth, smooth. The tachometer is useful as my feet and ass are no longer accurate measures. Bike pulls very well. Plugs a beautiful tan colour. Idle at 1000, returning predictably and promptly.
    As I said earlier, I've never ridden another airhead. But, I'm pretty sure this one is now sorted. Not quite as smooth as my R12GSA, but pretty close for gear that is 30 years older.
    Many thanks for the help and suggestions.
    Forecast is for rain and snow for the next three days.
    :muutt:muutt:muutt:muutt:ddog:ddog
    #37
  18. Yipcanjo

    Yipcanjo Adventurer

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    My apologies for resurrecting this thread....

    I have a '78 R100/7 with the exact same symptoms. It idles great when cold, and then idles high when warmed up. If I shift down (engine braking) when coming to a stop, I can force the idle back down to normal. If not, the idle runs high -- probably in the 2.5k range or so (I don't have a tach). I can also release the clutch a bit to get the RPMs back down.

    Anyhow, I guess my next step is to adjust the Air/Fuel mixture and the Idle Adjustment screw. After getting the bike nice and warmed up (20 min ride or so), what's the best way to tackle those adjustments? And which do I do first?

    Thank you...
    #38