Question about 2003 Yamaha YZ 125

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Hi got yz 125 2004 starts first kick evry time but soon as you rev it up at high revs it cutts out and when u ride it soon as the vavles open it cuts out wont bump but if you put the clutch in and kick it it starts?? ive cleaned the carb 10 times new plug ect any ideas there is a good spark changed the fuel and plug cheaked the piston and ring fine air fiklter new ?? am stuck it starts first kick and tick over all day but when u rev it hard it dyes!

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  • daveleech69 Mar 21, 2011

    how do i check the fuel level in the bowl ? cheers is thz the float needle ?

  • daveleech69 Mar 23, 2011

    hi checked float height ok it ran ok takes off but when u hit the vales it dies then started spultering on then dies hold clutch kick it over first kick but will not bump start, but now it wont start at all goes to start but doesnt now. used to start first kick my m8 has got same bike so iv tryd cdi and ht coil no luk any ideas

  • daveleech69 Mar 24, 2011

    u no the little plastic cap on the bottom of the floats in the bowl i think that may of been push on to hard and wont let the floats drop rite down do you need it in there? it sit in the bowl could that hav out to do wif it? not leting the floats drop all the way ill let u know!! regrads davey

  • daveleech69 Mar 24, 2011

    hi again ive try my m8s carb still no luck wont start , when i checked the piston it had black suit all over it even under the ring the hole thing was nearly black could it be top end rebuild or new piston no marks on the bore am getting sick now it did start first kick now wont start ive try cdi ht lead carb,, help.....

  • daveleech69 Mar 24, 2011

    wat about the startg isue as ive tryd a diffrent carb regards

  • daveleech69 Mar 25, 2011

    now am thinkg reeds???? got spark checked ht lead cdi ,carb and now it wont start how do i check my reeds (test ) or wat am i lookg 4?? davey

  • daveleech69 Mar 25, 2011

    happy man now i took the reeds houseg and reeds apart clean them up with carb cleaner its alive regards davey boy leech ovingham crazzy hourse

  • daveleech69 Apr 04, 2011

    hi agin still won thought it was reeds but wasnt ive now tryed new piston cdi carb staor plate coil still wont start it burns the fuel as it smokes from the exhurst but wont fire help

  • daveleech69 Apr 04, 2011

    still no luk wont start ive now put new piston ,staror plate cdi coil plug carb but still wont fire up it is burng the fuel as it is smokeg from the exhurst pipe help..



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Check the fuel level in the bowl of the carb, if it's set too low when the engine revs the bowl empties and the engine cuts out. Also check the fuel lines and the filter, if they are partially clogged the fuel flow to the carb is too low, the bowl empties and, again, the engine cuts out.

Posted on Mar 21, 2011

  • 5 more comments 
  • Azrael SRL Mar 21, 2011

    You measure the position of the float that moves the needle. Follow this

  • Azrael SRL Mar 23, 2011

    Something is wrong with the carburetor: either a gasket is missing or one of the components has been damaged when you reassembled it. Take it apart again and check every single jet, orifice, gasket and air and fuel channel in it.

  • Azrael SRL Mar 24, 2011

    Y es, that might be it - you will need to replace the entire float mechanism, valve included.

  • Azrael SRL Mar 24, 2011

    The black stuff is carbon deposits - the mixture is too rich: lower the level in the bowl and readjust the idle.

  • Azrael SRL Mar 24, 2011

    Caused by bad mixture - check the choke and redo correctly all the settings of the carburetor.

  • Azrael SRL Mar 25, 2011

    You put the reeds on a can, seal it all around and you pump air in the can - if they open only when you pump then they are ok at admission. Flip the over and try to pump air - if you can't then they are ok at compression.

  • Azrael SRL Apr 04, 2011

    If it makes smoke then something gets burned, which means that the spark is there, just not strong enough - check the wires and the grounding connections.



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