Dangers of running lean

Discussion in 'Land of the Rising Sun: ADV Bikes from Japan' started by Rigbot, Jun 27, 2013.

  1. Rigbot

    Rigbot Adventurer

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    I recently installed a Termi full system on my 2003 Ducati Multistrada 1000. I had planned to have my ECU flashed to "full Termi" specs and/or get it Dyno tuned. Now I'm not so sure I want to spend that extra $. The bike is running fantastic. I have not checked the A/F ratio but the throttle response is much improved, it feels more powerful, doesn't pop on deceleration and so far it hasn't run any hotter than before. So, my question is: Will this damage my bike? I've searched this site and the web and read over and over about how running lean will cause the bike to get hot and damage the engine. Is heat the only concern here? If I keep a close eye on the temp gauge and keep it below 330ish am I really risking damage? If so, what kind exactly? Air cooled bikes have a very wide operating temperature range, and are less prone than water cooled bikes to overheat. How reckless is leaving the fueling stock with a full exhaust? Anyone here do it, and if so what were your results?

    Thanks,
    Rigby
    #1
  2. ronandkat

    ronandkat Been here awhile

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    Theres plenty of conclusive evidence and experiences that running lean will damage an engine.. How much damage depends on the time frame and how lean it actually is. Im not fmailiar with the Ducati, but basically I always did a plug check when making adjustments or adding / subtracting parts. I simply installed new plugs at the time, did some runs, pulled the plugs and checked color.

    There is the scenario, that since it runs so well, and doesnt pop on decel, that maybe it was actually running a tad rich in stock form, and that you possibly brought it into line by adding the pipe?
    #2
  3. Schlug

    Schlug JockeyfullofBourbon

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    put something on and stay in that position.
    Which would make it the very first bike in the history of modern motorcycles to come rich from the factory as opposed to lean as hell in order to make emissions.

    Chances are the opened exhaust on its own will accomplish little and if you haven't opened your airbox up or installed a high flow air filter you've not done much at all.

    Sure, the bike can get rid of more exhaust. But it can't take in any more air. Chances are all you've really done is lost low end and made room at the top end, but such a small amount you be hard pressed to feel it.


    Probably sounds wicked good though, huh?

    [​IMG]


    [​IMG]

    [​IMG]



    Holed pistons due to lean condition.
    #3
  4. Rigbot

    Rigbot Adventurer

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    I did a K&N panel filter. Thinking about velocity stacks and pod filters but I'm sure you'd say they would rob even more midrange and sacrifice rideabity without any real gain. They seem to work on other bikes so I may try them anyway.

    Regarding the photos, I understand that there is a 99% chance I'm running lean as hell. I also don't dispute the fact that running lean can cause catastrophic engine damage. Call me dense, but I just want to understand the actual process that causes the damage. I know lean bikes run strong and clean right until they hole the piston. But other than heat what actually causes the damage? Say a person rode 10 minutes to work each day and lived in Alaska where the hottest it ever got was 50 degrees Fahrenheit. They are running their bike super lean due to a faulty reading or mental error. Like 15/1 lean. So the bike never gets above 200 Fahrenheit because of the cold ambient temps and short run time. Is this bike going to suffer damage because of the lean condition or live a long a happy life? If there will be damage despite the low engine temps what exactly would cause it? BTW, I'm taking my bike to a dyno tomorrow to find out my A/F ratio and torque curve. Presuming it will be lean, how lean is too lean. Is there something other than temperature to worry about? Just trying to learn here.

    And yes the bike sounds glorious. I'd rather it be quiet so I could banzai neighborhoods without getting the cops called on me, but the power is addictive and not just a figment of my imagination. Adding just a slip-on made it run stronger and the header and filter just made it even more awesome.
    #4
  5. Schlug

    Schlug JockeyfullofBourbon

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    put something on and stay in that position.
    There are two things that happen when you run lean.

    First, you make a hell of a lot of excess heat. The flame front is slow and even and cooler when the bike is tuned properly. If the F/A mix is lean, the flame front is fast and really hot. So you have generated a lot of extra heat.

    But what you've also done is introduced extra oxygen into the cylinder. A good F/A mixture uses up all the oxygen in the cylinder and burns most of the fuel. If you don't burn up all the oxygen because you have introduced too much of it you will create an oxygen rich environment which we know is also very hot.

    This is murderous to metals, who don't do well with heat and oxygen. Think cutting torch.

    You can cut valves, hole pistons, and wreak havoc on your spark plugs.

    The very FIRST rule when it comes to intake/exhaust/fueling is: If you can't be arsed to do ALL of the mods, don't do ANY of the mods. Don't open the airbox/exhaust without having a PC or jets in hand.
    #5
  6. TAMPAJIM

    TAMPAJIM Been here awhile

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    +1
    There's a reason why they been re-jetting carbs and changing EFI maps after breathing modifications for all these years. Those photos show it loud and clear.
    #6
  7. ronandkat

    ronandkat Been here awhile

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    #7