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Thread: What does "running lean mean"

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    What does "running lean mean"

    I have an 03 Volusia--just curious what "running Lean" means, and how you would know if your bike is running lean...Also, what are the effects of this on your bike, or your ide in general? Thanks.

  2. #2
    Miles of smiles We've stopped counting... asp125's Avatar
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    For optimum burn, the ideal air/fuel ratio is about 14.7:1 (approx 14.7 times more air than fuel). Anything less than that you are running rich, wasting fuel. Your exhaust pipe will have sooty black deposits, from incomplete burn of gasoline. More than 14.7:1 you have too much oxygen, and the burn is too hot, I forget the coloration though... brown/grey?

    Modern EFI computers automagically compensate for the A/F ratio. Carbs have a harder time with changes in oxygen content due to elevation.
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    Flirting With The Redline 4000 Posts! atonic's Avatar
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    Running lean means too much air in your air/fuel mixture. Causes your engine to run hotter than optimal. Can cause your pipes to turn 'blue'.

    In the extreme it can cause burnt valves.

    This condition is commonly caused by:
    1. Modified intake (pods, easy-flow filter, etc)
    2. After-market exhaust
    3. Intake leaks


    I'm not sure how it will effect your idle.
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    Flirting With The Redline yossarian's Avatar
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    A lean condition is the end result of too little fuel and too much air. Slightly lean conditions create drivability problems. Lean mixture burns hotter. Worst-case scenario: Lean conditions can and do destroy engines. Holes in the pistons, burnt valves and trashed main bearings are the direct result of lean mixtures.

    Rich mixtures are the end result of too much fuel and too little air. Rich mixtures waste fuel, contribute to carbon buildup and pollute the air.

    Typical Lean Conditions:
    - Poor acceleration; the engine feels flat.
    - The engine won't respond when the throttle is snapped open, but it picks up speed as the throttle is closed. (A too-large main jet also mimics this symptom.)
    - The engine runs hot, knocks, pings and overheats.
    - The engine surges or hunts when cruising at part-throttle.
    - Popping or spitting through the carb occurs when the throttle is opened. Or popping and spitting occurs through the pipe on deceleration with a closed throttle.
    - The engine runs better in warm weather, worse in cool.
    - Performance gets worse when the air filter is removed.

    Typical Rich Conditions
    - Engine acceleration is flat and uneven and loses that "crisp" feel.
    - The engine "eight-strokes" as it loads up and skips combustion cycles.
    - The engine's idle is rough or lumpy, and the engine won't return to idle without "blipping" the throttle.
    - The throttle needs to be open continuously to maintain acceleration.
    - Black, sooty plugs, a sooty exhaust pipe and black smoke from the tailpipe that stinks of unburned fuel.
    - Poor fuel economy.
    - The engine works better when cold. Performance falls off as it warms up or the ambient temperature rises.
    - Engine performance improves when the air cleaner is removed.

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    Flirting With The Redline 2000 Posts! midknyte's Avatar
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    Quote Originally Posted by atonic View Post
    Running lean means too much air in your air/fuel mixture. Causes your engine to run hotter than optimal. Can cause your pipes to turn 'blue'...
    A certain amount of "blue"ing is normal, usually a few inches into the header pipe. "Too much" is indicative of running lean. Some pipes are double walled / shielded to prevent blue-ing though.

    Also to note, each pipe should have the same amount of blue-ing. One more-so than the other indicates a proble in one of the cylinders...
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    Flirting With The Redline kwr8728's Avatar
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    FYI, there are times when you want to run lean and times you want to run rich. mainly depends on throttle opening, and how well you can atomize fuel. Which that can depend on air velocity...

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    BBO Communications Liaison 5000 Posts! RockyMtnRoadRash's Avatar
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    Quote Originally Posted by Jpeluso8 View Post
    I have an 03 Volusia--just curious what "running Lean" means, and how you would know if your bike is running lean...Also, what are the effects of this on your bike, or your ide in general? Thanks.
    Your bike is running lean at idle. Truuuuuust me. That's why it's a rabid bastard to get started on cold days and why you have to use the choke so much when starting out.

    The good news is, the mixture's darn near perfect higher up the range, so your bike has great grunt and decent power throughout the range. Plenty of guys do change the fuel properties but on a good day they get maybe 5 more hp and obliterate their fuel economy. Apart from the whole cold start thing, the Volusia doesn't really warrant monkeying with in the fuel/air department (Caveat: New pipes or breather units may dictate changes)
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    Quote Originally Posted by RockyMtnRoadRash View Post
    Your bike is running lean at idle. Truuuuuust me. That's why it's a rabid bastard to get started on cold days and why you have to use the choke so much when starting out.

    The good news is, the mixture's darn near perfect higher up the range, so your bike has great grunt and decent power throughout the range. Plenty of guys do change the fuel properties but on a good day they get maybe 5 more hp and obliterate their fuel economy. Apart from the whole cold start thing, the Volusia doesn't really warrant monkeying with in the fuel/air department (Caveat: New pipes or breather units may dictate changes)
    Thanks Rocky...you seem to have some insight into my VL alright...so then my header pipe is definitely disolored, it has turned a "golden" type color...not terribly dark but noticeable...this normal, or indicative of a problem? As far as the bike when running...I do have a slight hesitation at only partial throttle, but actually seemed to have gotten better with some Seafoam (bought a used bike and figured the carbs needed some cleaning). Other than that bike seems to run ok... I noticed my key getting hot, but talked to others who have said this is normal where there ignitoon is on the Volusia's...there you go, gave you all symptoms of my bike!

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    Thanks everyone for explaining this to me...glad to see I can ass questions that EVERONE else knows the answer to here, and not feel too incompetent.

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    BBO Communications Liaison 5000 Posts! RockyMtnRoadRash's Avatar
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    Quote Originally Posted by Jpeluso8 View Post
    Thanks Rocky...you seem to have some insight into my VL alright...so then my header pipe is definitely disolored, it has turned a "golden" type color...not terribly dark but noticeable...this normal, or indicative of a problem? As far as the bike when running...I do have a slight hesitation at only partial throttle, but actually seemed to have gotten better with some Seafoam (bought a used bike and figured the carbs needed some cleaning). Other than that bike seems to run ok... I noticed my key getting hot, but talked to others who have said this is normal where there ignitoon is on the Volusia's...there you go, gave you all symptoms of my bike!
    My second bike was a 2004 Volusia that we put 15Kish miles on in the year I had it. If the seafoam fixed you up you should be good. Some minor goldness is pretty normal. The hot key is indeed normal, and a function of the damn fool placement of your keyhole relative to the radiator.

    As for the hesitation, I would also check your plugs. It's pretty dang easy once the tank's off and my experience is that a lot of doofus owners (of which there are many for the volusia because it's pretty and cheap) don't do the plugs because they're skeert (an incident with a non-starting virago springs to mind. 15 minutes of plug changing later the no-spec plugs were in the garbage, new manual-spec ones were in and it ran like a champ.) Similarly, a valve check and adjustment is pretty easy apart from the awful bastard inaccessible tiny bolts that hold you valve covers on.

    In general that bike is a low-maintenance tank. Put oil in (buy a jack from Sears or Pepboys for this and basically all maintenance) check your tire pressure and fiddle with the handlebar position and rear shock adjustment until it feels right for you and you're golden. You'll be amazed at the handling and ride improvement if you change out your tires to ME880s when the current ones wear down (assuming you haven't already.)

    The only serious annoyance I ever had with the volusia was when the choke got jammed in and it became impossible to start on cold days. That sucked royally. Oh, and the time I left the key turned on for a week and turned my battery into a brick... but I suppose that's not the bike's fault so much as the loose nut between the seat and bars.
    -RMRR
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    It's vitally important to know the correct name for all parts of a vehicle so that you can curse them accurately when they break.

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