Home Forums Briggs & Stratton 4-Cycle Racing Briggs LO206 Engine running lean

This topic contains 5 replies, has 4 voices, and was last updated by  William Weiler 5 days, 4 hours ago.

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  • #84526

    William Weiler
    Participant

    I looked at my plug a month ago and it was grey/white so I put the carb needle up a notch to raise the needle. Then I took apart the carb and sprayed it out and got the part numbers on the jets and confirmed it was stock. Last weekend after running I checked the plug and it was bone white, way too lean. I raised the needle more. The engine also did this weird thing where when I started it full choke, if I lowered the choke bar, the idle went way up. When it was hot this problem went away and it seemed normal. The engine is used but I don’t want to blow it up. Can anyone diagnose what’s wrong? The temperature last weekend was in the 90’s, but shouldn’t that richen it up?

    TonyKart 401s LO206
    Masters Class
    Morgan Hill, CA

    #84527

    FREDDY SANDOVAL
    Participant

    You can’r read the spark plug like on a 2 stroke and expect it to be brown or darker. these motors are just like a car motor.

    The idle issue you may be having is most likely a vaccumm leak at the intake manifold or gasket, the engine cannot breath anywhere else other than the air filter area (front of carburetor)

    Run that engine, let it idle on the stand, spray small amount of car/brake cleaner around the suspected air leak area, and see if anything changes after you spray.

    #86395

    William Weiler
    Participant

    When I raced at Dixon, I saw the rubber cover on the throttle cable at the top of the carb was cracked pretty bad, so I taped it up with electrical tape. Do you think air could enter the carb at this spot? That might explain the weird idling problems. I will see if it happens again with the rubber cover taped up.

    TonyKart 401s LO206
    Masters Class
    Morgan Hill, CA

    #86481

    Clark Gaynor Sr.
    Participant

    First, both of our 206’s idle high when we first start them.  But after a minute or so, they settle down and are fine.  I don’t know why, nor do I care.  I’m only concerned how they run on the track and hot.  My kart doesn’t like to idle at all, and I’m OK with that too.  Our ultra high tech automobiles don’t always behave properly when they’re first started.  Why would you expect a very inexpensive, low tech, industrial, rototiller motor to do better?

    The rubber boot thing is a none issue to the best of my knowledge.  It simply holds the outer throttle cable in the top of the carb.  We’ve run engines with and without them and I never gave it much thought.

    William, just relax and enjoy.

    Clark.

    #87483

    George Young
    Participant

    Hi William, now that the season is over I may have some help for you, all be it a little late. I have a little experience with the 206 and can tell you a few things that may help.

    You can read the plug easily just use a new plug to get accurate info. The boot does matter and is definitely an important part. Yes it can produce an air leak. The low speed jet is so small make sure it is clean and clear. A sonic cleaner works very good with distilled water and a mild water based cleaner. The needle is for low to mid and does not “cross over” to the high speed system. Although the needle can be an indicator as to the direction you may want to go on the high speed. Now for the high speed – remove the carb and remove the bowl. With the carb upside down measure from the lip of the body going around the float to the top of the float. Using a caliper set it to .87 inch. Make sure both sides are measuring the same and are not uneven. High speed can be adjusted by the float setting. Yes it works. Short tracks and rich setting at about .83  to .84 and lean setting to .92 to .93 – keep in mind the carb is upside down. Basically you are starving the engine slightly with a low (right side up) float setting.  The engine loves to be lean on the top end, but if course there is a limit. Short straights and short twisty tracks on the richer side maybe like Davis. Longer straights and faster track leaner like Sonoma or maybe Atwater( Atwater being a compromise between the long straight and the slow tight corners) In conjunction with precise valve settings a fair amount can be gained. Also make sure the air needle adjustment is about 1-1/2 turns to start out with. Remember that it lets air in, the further out the more air is entering the low speed system. The needle in position 3 – numbered from the top of the needle with the top being #1 so  #3 is in the middle. Experiment and learn.  You may private message me and I can help a little more or clarify what I write. By the way, I have never had an idle issue in the 3-4 years my son and I have raced the 206.

    • This reply was modified 1 month, 3 weeks ago by  George Young.
    #89326

    William Weiler
    Participant

    George,

    I just read your post, although I will have to study it. I don’t have idle issues anymore, I don’t know why. Also, I checked my valves and my exhaust valve was tighter than my smallest gauge, which is 0.001. I set it to 0.002. This is the first time I checked it. Not sure why it was so tight.

     

     

    TonyKart 401s LO206
    Masters Class
    Morgan Hill, CA

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