yz250 2000 rattle

Discussion in 'Motorbike Technical Discussion' started by Josh-yz250-2005, May 22, 2006.

  1. Here is a mind bender for you. My buddies bike is goofed and I'm
    stumped.

    Yz250 2000, good shape. Brand new bottom end, new crank bearings, new
    hot rod crank connecting rod all that good stuff. (shoved a rock
    through the bottom end a year ago and it was a great time to replace
    all the bearings. New piston (new cylinder). New clutch.


    Put the bike back togeather after rebuild and it ran great. for about
    30 hours of leisure bush riding and track riding. Then "friend" has it
    pinned and it just bogs and dies. Since then replaced rings (which were

    goofed) and it sounds supper clackity. Pulled head/cylinder measured
    tollerancs on crank and assorted parts and everything is in spec. No
    wear on cylinder to suggest bad piston (leanover). Definatley sounds
    exhaust related.


    I did the old trick (to test) of hooking a drill to water pump and
    remove spark plug to listen if crank was wacking around or piston, no
    result. Bike is impossible to start (caveman push start only) and it
    sounds horrible (very knocking, no grinding, and lots of vibration).


    So again, pulling piston and checking tolerances. Case is clean (no
    filings). Carb is the same as it was before when it ran great so I'm
    leary to start monkey work on that one.


    The powervalve is the only one that I've done nothing with. When the
    bike does start it sounds like the effect/problem is in the exhaust. Is

    this a common thing? Or am I looking at something electrical like bad
    timing?


    Help this poor fool please.


    yz250-05-josh
     
    Josh-yz250-2005, May 22, 2006
    #1
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