1998 Yamaha Wolverine 350 4x4 fuel problems

Discussion in 'Shop Talk' started by billyj, Dec 22, 2005.

  1. billyj

    billyj Well-Known Member

    Messages:
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    Jan 25, 2005
    Location:
    Central Louisiana
    Bought this machine reasonable knowing it wasn't running right. Since it had been setting up for sometime, I thought cleaning the Carburetor would do the trick. Sure enough it had a good coating of gunk inside.
    Prior to pulling the carb, it would run, but had what I call a back fire through the carb. After cleaning, it ran smooth so I put everything back together and took her for a spend.
    After the engine warmed up, it started running rough on acceleration but would not bog on an uphill grade. Finally it would not accelerate at all, but will idle smooth as you could want.
    Next day.
    Took her for another spend runs fine for a bit, then a repeat of what happen as mention before.

    Here's what I have. It's fuel mixture is an aspirated 34mm Mikuni CV carburetor 4k B100.

    Weigh in on this if you like, any help with ideas and input would be greatly appreciated.
    Here is a web site with an exploded view of the carburetor and a parts list.

    http://houseofmotorcycles.bikebandi...~mscssid~E79D1CKDB0XX9NHA9FMFTLLENE6AC2CA.asp
     
  2. justmyluk

    justmyluk Well-Known Member

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    Apr 28, 2005
    Location:
    North Carolina
    One thing you might check is the butterfly on the choke. If the choke isn't opening all the way when it's warm, it could cause these symptoms. A cold engine runs fine with the choke on but a warm engine will run rough if the choke or butterfly is sticking.
     

  3. gspig

    gspig Well-Known Member

    Messages:
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    Dec 11, 2002
    Check your tank vent tube. Sounds like fuel starvation. I have a similar machine '94 350 Big Bear, there is an idle mix knob under the fuel bowl on the carb, you may be able to fine tune with that.
     
  4. TheBlueOne

    TheBlueOne Well-Known Member

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    Jul 2, 2004
    Location:
    Michigan
    Drain the tank all the way and watch for stuff to come out (sediment). After the tank is clean refill with fresh 87 octane gas. Pick up an inline fuel filter (clear plastic one) from a bike shop for about $3 or so. While there get a fresh spark plug and install that also. What condition is the air filter in? Stock exhaust or aftermarket?
    After that we get into jetting.....
    I have a '95 Warrior BTW, same air cooled 348cc motor but it's 2 wheel drive.
     
  5. billyj

    billyj Well-Known Member

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    Jan 25, 2005
    Location:
    Central Louisiana
    TBO, I have cleaned tank, new gas, cleaned carb, new plug, didn't change filter just cleaned it and put a lit coat of oil as recommended. I am baffled
    by the fact that it runs perfect until the engine get hot.
     
  6. justmyluk

    justmyluk Well-Known Member

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    Apr 28, 2005
    Location:
    North Carolina
    Have you checked your coil?? It could be breaking down when it gets hot and causing a weak spark.
     
  7. billyj

    billyj Well-Known Member

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    Joined:
    Jan 25, 2005
    Location:
    Central Louisiana

    Thanks. I did not check the coil