yz400f ?

5 replies to this topic
  • Lawrence Olson

Posted May 11, 2016 - 05:45 PM


I have a 99yz400f. Bike has been giving me a problem :banghead: \. During the last ride towards the end of the ride i notice a loss in power and it was popping :facepalm: . Since then i have cleaned the carb and got it running nice no popping. takes a few kicks to start. but still have a no power problem. i know its a four stroke but think of it ths way i have no powerband. Almost like its in limp mode only applys so much power. could this be a cdi issue?

  • downonmonday

Posted May 11, 2016 - 10:02 PM


When was the last rebuild?

  • grayracer513

Posted May 12, 2016 - 06:21 AM


Check your cam timing. 

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  • toten

Posted May 12, 2016 - 07:19 AM


+1 on cam timing. Also check valve clearances, they can lead to problems with hot starting.

  • Lawrence Olson

Posted May 12, 2016 - 03:56 PM


:thumbsup: thanks guys for the replies. it starts just fine when hot. runs and idles great. if your a mechanic think of it as its in limp mode :lame: 


  • Lawrence Olson

Posted May 14, 2016 - 12:49 PM


forgot to add one thing a few times i would go to kick it over and it would act as if i had the decomp lever pulled. when i didn't. so i think yo may have something there with a valve problem :rolleyes:

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