snapper backfire

Discussion in 'Mechanic and Repair' started by Differential, May 1, 2010.

  1. Differential

    Differential LawnSite Member
    Posts: 135

    I'm running a snapper 21 with the wisconsin robin 5hp engine. Sometimes when I stop the mower to empty the bag, it will backfire when I restart the mower.

    It only backfires once, on the first pull, after i've re-started it. The mower has been maintained impeccably, and runs really well. No smoke, runs smoothly, plenty of power, etc...

    Anyone know why I get that backfire after a quick break to empty bag?
     
  2. topsites

    topsites LawnSite Fanatic
    Posts: 21,654

    Can you leave it idling while you empty the bag?
     
  3. Differential

    Differential LawnSite Member
    Posts: 135

    With this model, there's now way to safely unload bag with engine idling.
     
  4. STIHL GUY

    STIHL GUY LawnSite Fanatic
    from CT
    Posts: 5,225

    try to slow down the RPMs and let it cool down a bit before turning it off. dont go from full RPMs to stop
     
  5. Shasta Lake Landscaping

    Shasta Lake Landscaping LawnSite Senior Member
    Posts: 436

    I just got one of these mowers today out of a pile of junk that was to be hauled away at a clients house. After I change the oil and do regular maintenance I'll run it and see if mine does the same.
     
  6. Keitha

    Keitha LawnSite Member
    Posts: 4

    The back fire is the fuel mix hitting a hot spot someplace, could be a piece of carbon in the head or exhaust.
    I agree try to let it cool down a bit before shut down.
    Fix may involve cleaning piston top, cylinder head and muffler.

    Keith
     
  7. Differential

    Differential LawnSite Member
    Posts: 135

    I've been trying to let it idle down for a few seconds before i shut it off to empty the bag. I haven't had a backfire since I started doing this.
     
  8. Tony O

    Tony O LawnSite Member
    Posts: 4

    Differential,
    I have the same mower set-up you do and the same identical problem you just described. I purchased mine used from CL, hadn't been used commercially. I had this problem since day one but other then that it's been
    a great mower smooth and plenty of power. I just acquired a Tru-cut rotary mower and I'm thinking of swapping out the Honda 5hp for the Wisconsin Robins.
     
  9. Shasta Lake Landscaping

    Shasta Lake Landscaping LawnSite Senior Member
    Posts: 436

    Mine does not backfire, although I did decarbonize the cylinder head when I did the other maintenance things. Where can I get a manual for the engine? I found the snapper manual online but couldn't find the Wisconsin manuals.
     
  10. Differential

    Differential LawnSite Member
    Posts: 135

    I got these from Subaru Robin...
     

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