How to diagnose Lawn Boy mower problem?

Discussion in 'Shop Talk' started by clovis, Aug 1, 2009.

  1. clovis

    clovis Well-Known Member

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    I have an older Lawn Boy Silver Series mower with the 6.5 horse, 2 - cylcle engine.

    While some dislike the LB Silver models, this mower has run like a champ since I bought it new in '97. Up until this year, it has run just like the day I brought it home in the box.

    It still purrs away when it is running, and almost always starts on the very first pull.

    The problem that I am having is that it dies on occasion. It will be running perfectly, and then dies like it is out of gas, but without the starving of on-off-on-off when it finds just another drop of fuel. It'll run perfect one second, and the next second, it is dead as a door nail.

    I normally run Amoco or Shell gas, that is advertised without ethanol, but have run cheap pump gas in years past, when I didn't know any better. I have ALWAYS used LB brand oil in the cans, and mix as if I were running a controlled experiment, not just mixing with the attitude of "good 'nuff".

    A couple of symptoms that may or may not be a factor:

    This mower, since new, has leaked fuel out of the top mounted exhaust, and onto the top of the deck when in the shed. If you leave fuel in the tank, there is a good chance that the tank will be empty a week later due to this leak. I have inspected the mower again and again, but cannot find any leak in the fuel lines...it has to be coming from the muffler.

    Sometimes, but not always, on cold starting, the engine will race to high RPM's before settling back down to normal RPM's.

    Sometimes, and I am not 100% sure on this...it acts like it is flooded when I try to restart it. It seems like throwing on the choke that it is easier to restart.

    It also seems, and I could be imagining this, that the mower is prone to dying when it is pulled backwards. Not every time, but it seems like it dies a little more often pulling it backwards than it does just pushing it forward.

    As well:

    I appears that I have plenty of blue spark at the plug, which I have checked several times.

    It also appears ever so slightly that I have a bit more smoke on start up after it dies than it should.

    I suspect that the fuel is leaking into the cylinder. I just don't know where or how.

    Any ideas? On-line forums that you might know of? Manuals or books that you can suggest?

    I just need to figure out where to start with this mower.

    Thanks in advance!!!!!!!!
     
  2. Wis Bang

    Wis Bang Well-Known Member

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    Two cycles still have a carburator and if fuel is leaking when it is sitting, the float & needle is gummed up in the open position and letting the fuel run thru. Run it dry and it won't leak. Clean the carb [seafoam] and that should free up the float and needle valve.
     

  3. zant

    zant Well-Known Member

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    Check the rings too and make sure all block bolts are tight..
     
  4. Windy in Kansas

    Windy in Kansas In Remembrance

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    Once the mower has died as described will it immediately restart or does it need to set awhile?
     
  5. clovis

    clovis Well-Known Member

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    It seems to be a little hit and miss...no pun intended.

    Mostly, it seems like it will restart right away. If it is any trouble to restart, I have found that putting it in choke will cause it to fire, then pull the lever into rabbit mode, and it runs just fine until it dies again. That might be 2 minutes or 13 minutes later.

    I have wondered if the engine was flooding out when it dies????? It does not rev any higher before it dies though.

    One second it is running fine, and the next second, it is deader 'an four o'clock.
     
  6. clovis

    clovis Well-Known Member

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    Wis-

    Can I run Seafoam through the engine, as an additive to the fuel mixture, or do I need to remove the carb assembly and soak/clean it in a can of Seafoam?

    Thanks!!!!
     
  7. Wis Bang

    Wis Bang Well-Known Member

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    I'd soak it. Lawn Boys were good old Mowers; My dad got a few from his friend who owned the local hardwear store [they were a LB dealer] they were trade ins and he got them all runing. He gave one to a friend of mine, it was 20 yrs old and he's been using it for over 20 years.