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6 HP Briggs loses power

Discussion in 'Mechanic and Repair' started by agreif, May 18, 2004.

  1. agreif

    agreif LawnSite Member
    Posts: 3

    OK, I'm a newbie to the site, so be gentle. I just picked up a 5-6 year old self propelled Murray lawnmower from my boss that he has had trouble with and was tired of messing with. It has a 6 HP Briggs. Here is the problem. He says it will go for about 20 minutes and then start to lose power down to an idle level. He's taken it in and I guess they replaced the carb float. I got it last night, emptied the gas tank, put some carb cleaner in the carb and some injector/carb cleaner in the tank and let it sit. I haven't experienced it yet, but figured you guys might be able to point me in the right direction. I haven't pulled the plug, but can't see it causing this problem specifically (although it probably would help). It's got to be something fuel related I would think. I'm hoping the new gas will do it, but I'm not sure. Filter looks good, not gummed up.


  2. martinw

    martinw LawnSite Member
    Posts: 23

    If I understand this correctly you are saying it runs for about 20 mins. then it dies out. It makes me think the problem is related to when it gets hot rather than fuel system. I'd do a compression check on it and see what happens from there. Just a piece of advice too while you have the mower set up now, I'd go ahead and check/change the air filter, spark plug, do an oil change and maybe sharpen the blade (pretty much all routine maintance, but it isn't a bad idea and elimates the filter and plug from being a problem too).
  3. Molerj

    Molerj LawnSite Member
    from Ohio
    Posts: 39

    Don't rule out the gas cap, altho 20 min. sounds like a long time. When it starts to die out try loosening the cap.
  4. agreif

    agreif LawnSite Member
    Posts: 3

    Ok, went home last night and started it and it would die immediately after it started. I could get it started by throwing some carb cleaner down the carb, and it would run until it had used that up as fuel (~ 3 seconds). When it primed I could see fule coming out, but I couldn't really tell when it was running if it was pulling it through. So I took the whole thing apart (big deal for my lawnmower rookie hands) and pulled the bowl off the carb. It looked the way oil does in water, I guess some of the gas had varnished. So I emptied that out andblew thru all the ports to make sure they were free, buttoned her back up and she ran like a champ. Didn't have the losing power problem. I'll keep the gas kap in mind though.


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