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Thread: 1988 Yamaha bigbear 350 boggs down with no power

  1. #1
    Join Date
    Apr 2020
    Ontario Canada

    1988 Yamaha bigbear 350 boggs down with no power

    Hi everyone,

    I was on this site about 15 years ago but forgot my original login. Now I am Happy to be back again.

    I have a 1988 yamaha bigbear 350 4x4. It was running fine, then all of a sudden, my exhaust would glow red hot and would loose power. It will idle no problem, but as soon as you roll the power on, there isnt much there.

    I have verified the following to be within specs.

    - compression is good (according to a good friend)
    - leak down is very acceptable.(according to a good friend)
    - timing is right on. (According to a good friend and I have verified myself)
    - cleaned air filter

    Here is what I have replaced so far:

    - carburator intake boot
    - carburator (chinese carb off amazon)
    - spark plug

    * I still have the original Mikuni carburator, but I had to drill out the low speed air screw as it was jammed solid in the housing. I have not purchased a carb rebuild kit for it yet, but it is an option I am willing to try. Just keep in mind that the problem started even before I changed the carburator.

    What I have noticed:

    Multiple sparks during complete cycle ( much more than just 1 spark per cycle)

    What I have also tried:

    - removed all of the handlebar and thumb warmer electrical that were installed by previous owner.
    - baked the CDI In the oven.

    I have recently purchased another CDI off a 1987 bigbear and waiting for it to arrive.
    If this doesnt solve the problem, I will replace the coil and/or stator/pulse generator next.

    I dont know what else the issue could be.

    Has anyone ever had this problem before?

    Please help!

    Thank you,


  2. #2
    Join Date
    Feb 2011
    Sounds like a carb issue to me. i have had a few of those models and never had a problem.... those aftermarket carbs imo. are junk.
    our original 85 we bought new, 2 - 86 police specials
    250r dust runner
    04 Yamaha kodiaK 450 snowbuster ! Brute Force 750 dust collector .
    Bunch of es stuff I been buying for next builds....
    Gone but lives on in my aching body the mighty 350x collection . A Beat 85 es im gonna rebuild

  3. #3
    Join Date
    Jul 2009
    South Florida
    Make sure your exhaust is flowing freely .
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    Performance Shop is Open PM me for Service

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