Question about 2003 Yamaha YZ 125

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Still wont stat new piston plug storor cdi coil no luck help

Posted by Anonymous on


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So you've tested a spare spark plug sitting outside grounded to cylinder and you defintely have good spark?
If it getting fuel? Is the enricher (choke) working?l

Posted on Apr 04, 2011

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  • Anonymous Apr 05, 2011

    yes geting fuel new piston new coil new cdi nowt at all just wont start ?

  • Anonymous Apr 05, 2011

    and it is burng the fuel as its smokeg from the exhurst but jusy wont start?

  • Neil McRobbie Apr 05, 2011

    Any chance the timing is incorrect...not sure on your model...but the sensor to trigger the ignition perhaps bent so timing is off?
    No chance a bad intake leak....on the manifold...or crank seals leaning out the mixture?


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Are you getting a spark?
if so then check/clean your carb
if you have done this then remove the spark plug and put you finger in the hole in the head and try to kick start the bike are you getting compression? when you kick the bike you finger should be sucked into the hole.if this dosnt happen then the piston ring has gone needs repalcing
if you have done all this and there no spark then check the magneto for rust and that the sensor hasnt gone o/c if there is rust on there clean the pads with a piece of sand paper(GENTLY)
if there is spark and it wont start then check the air box also while i think of it the fuel ratio should be 32:1 thats 32 parts fuel to 2 parts oil

the thing with 2 stroke engines is they need fuel air and spark and they work

Hope this helps


Posted on Apr 04, 2011

  • Anonymous Apr 05, 2011

    yes good spark getg fuel new piston rings new cdi new coil ? still nowt its burng the fuel as its smokeg

  • john morgans Apr 05, 2011

    have you tried sparying inside the air box with easy start to see if the bike will actually start?
    noticed that you said that the bike has got new piston rings etc did it start before you did all this work?



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sounds like oxidization on your timing plate take it out and clean it with a peice of sand paper

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Hi and welcome to FixYa,

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Good luck and thank you for asking FixYa.

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