Moe power, moe power!

Discussion in 'Mechanic and Repair' started by LawnTroll, Aug 17, 2007.

  1. LawnTroll

    LawnTroll LawnSite Member
    Messages: 5

    I've finally got an old B&S 8HP ride-on mower engine going fairly evenly. It no longer 'hunts' and starts OK, but it doesn't seem strong. The least little stress and it slows, and some white smoke shows up momentarily. What should I adjust next, in order to strengthen it, or is this a sign of general wear?
  2. topsites

    topsites LawnSite Fanatic
    Messages: 21,652

    Have you tried running synthetic oil and super unleaded?
    Not sure what to tell you on grade, possibly the same as what you got in it now.
    But for fuel, try shell / bp / amoco / texaco premium, high grade quality stuff.
    You might also try an autolite double platinum spark plug.

    If yours uses the Champion rj-12yc, then the autolite equivalent would be app-5224 (yes pp = 2x platinum)
  3. Bill Kapaun

    Bill Kapaun LawnSite Senior Member
    Messages: 965

    Running premium fuel in an engine that has trouble making a 7:1 compression ratio isn't going to do a thing.
    May be a dose of fuel system cleaner in the gas tank might remove some gum & varnish on the carb Jet.
    Since you didn't post any engine numbers, it's impossible to tell if you have an adjustable jet in the carb or not.
    Simply running it may help. If the piston rings are gummed up, maybe a bit of "oil treatment" in the crankcase? You didn't give any history either, so I'm kind of assuming that the engine had been sitting awhile?
  4. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

  5. LawnTroll

    LawnTroll LawnSite Member
    Messages: 5

    The engine number is 92500(5). The last digit could be anything as its faded. The mower has been used fairly continually as far as I know. I do promote the use of synthetic oil in cars but I can't see it improving the power level in a mower.
    Is it correct to view what's happening as......any new demand on the engine is pushing it into an area where the balances of fuel and air are off?
    I will try the cleaners to see how they work.
  6. Bill Kapaun

    Bill Kapaun LawnSite Senior Member
    Messages: 965

    "The engine number is 92500(5)"
    That's the date code most likely or else you only have a 3.5 HP engine:)
    Need Model & Type#
  7. LawnTroll

    LawnTroll LawnSite Member
    Messages: 5

    How about: 191707-0640
  8. Bill Kapaun

    Bill Kapaun LawnSite Senior Member
    Messages: 965

    It appears you DO have an adjustable Main Jet.
    On the very bottom of the carburetor bowl, there should be a "spring loaded" screw.
    Try turning it in small increments (about 1/8 turn) and mow a strip. Repeat until you find the best performance.
    Out = richer
    Nominal setting is about 1-1/2 turns out from seated.
    DO NOT force the needle shut. Just light finger pressure to close.
    Keep in mind that you have a 15 year old engine. It may be simply getting "tired". The fact you get some white smoke, kind of confirms this.
    BTW, SOMETIMES a new spark plug can be very helpful. They're too inexpensive NOT to replace.
  9. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    You can try adjusting as Bill stated but check the throttle shaft and linkage for wear since this engine is sooo old.

    The above statement leads me to believe possibly the governor adjustment needs to be checked.

    1. Loosen screw holding governor arm to governor crank.

    2. Rotate throttle plate linkage from idle position to full throttle position. Note direction of rotation of the governor arm attached to the throttle linkage.

    3. Place and hold the linkage in high speed position.

    4. While holding the linkage in this position, Use a appropriate tool to rotate the governor shaft until it stops in the direction noted in step 2.

    5. tighten screw holding governor lever to governor crank. Torque to 35-45 in. lbs. (2.8-5.0 NM).

    6. Before starting engine, Manually actuate governor linkage to check for binding.

    If adjusting on the carb and the governor does not improve the lag when put under load the governor is most likely worn, The hole that the camshaft goes through gets elongated and will no longer function properly. The only fix in this case is a new governor.


    Good Luck
  10. LawnTroll

    LawnTroll LawnSite Member
    Messages: 5

    Useful, clear, consise info. Many thanks.

    The internet is both bad and good, like anything else, but a lot of the good comes from the interaction on its forums.



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