4 HP Briggs & Stratton Smokes

Discussion in 'Mechanic and Repair' started by mtwalls, Jun 28, 2004.

  1. mtwalls

    mtwalls LawnSite Member
    Posts: 4

    My 4 HP B&S is blowing black smoke out the exhaust. It is also running very rough and seems to be lacking poer. I took off the head and there appears to be some oil in the cylinder. It had gotten wet (left out in a torrential downpour by my son). What might be causing excessive oil in the cylinder? Nothing appears to be bent/broken and it starts on the first pull. Thanks!
     
  2. beransfixitinc

    beransfixitinc LawnSite Senior Member
    Posts: 592

    Would seem to sound almost (if you have oil on the head and didn't have it tipped foward) that you have overfilled the oil. Set your mower on level ground, remove the dipstick, wipe and reinsert, then remove again. If the oil level is above the "full" line by more than 1/8 inch, then you've got it overfull on oil.
     
  3. rockytopp

    rockytopp LawnSite Member
    Posts: 120

    Black smoke indicates that to much fuel is entering the cylinder. Float could be to high, but sounds more like wrong adjustment itself on the air mixture. I have seen to much fuel wash the carbon in the cyl. and it will look like oil when it is just diluted carbon. that would also exsplain the rough running. if not corrected it washes the rings down and results in galding the piston and wall of the block. rebuilding the carb might do it. Oil smoke is usually a nice blue and you can smell the diffrence between oil and gas in the air of the exaust. also running rich on gas will ruin a spark plug in a short while.
     
  4. beransfixitinc

    beransfixitinc LawnSite Senior Member
    Posts: 592

    The original post does not mention if the 4hp Briggs is a tank mounted carburetor, or a gravity feed float controlled one. Also, there is no mention as to its age. I'd still check for having the oil overfull.
     
  5. mtwalls

    mtwalls LawnSite Member
    Posts: 4

    Age is about 5 years old. Not sure if its tank mounted carburetor, or a gravity feed float controlled one. Will be looking into the carb this evening. I think its the carb as I haven't added oil since I changed it a couple of months ago. It had been running fine. And, I've been very careful not to overfill it. I've seen the effects and damage that results caused by overfilling. A neighbor just added an addtional 1/2-1 qt without draining the existing oil. Needless to say his lawnmower was DOA
     
  6. barnard

    barnard LawnSite Senior Member
    Posts: 618

    Bad gasket and diaphragm between tank and carb , allows too much fuel into carb. ( if its a tank mounted carb).
     
  7. Molerj

    Molerj LawnSite Member
    from Ohio
    Posts: 39

    One other thing to check is the air filter. Dirty filter will cause the rich running condition. Also an oil soaked filter, caused from turning the mower on its side will cause the same thing.
     
  8. mtwalls

    mtwalls LawnSite Member
    Posts: 4

     
  9. mtwalls

    mtwalls LawnSite Member
    Posts: 4

    Ok, Assuming I need to replace gasket and diaphragm between tank and carb (it is tank mounted) can anyone suggest how can find the part number for the kit? I've looked at the B & S site with no luck. Engine is 10G902-2139 4HP Quantum. Its possible it is the air filter as well. I took the air filter off and startee it and it runs better, but I still think its rough.
     
  10. beransfixitinc

    beransfixitinc LawnSite Senior Member
    Posts: 592

    Hmm.. that IS odd. Are you sure that you have the correct TYPE number? I show a range of 0015-0352 for types. Perhaps you have the wrong information for the TYPE?

    The gasket-diaphragm kit part number is 495770.

    Looking at the IPL, I almost have to assume that something is messed up on the documentation for this particular model.

    Sorry can't be of more help right now.
     

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