yzf 400 carb hesitation

5 replies to this topic
  • frig

Posted April 24, 2006 - 05:49 AM


I own a 1999 yzf 400 low hours looking for some info about low end carb hesitation or a dead spot int the
beginning of throttle, bike runs strong mid to high in talking to other riders sounds
like it always been a problem. I installed a hot shot from boysen and didn't notice a big difference. wondering about jetting pilot circuit? Is that were the
problems lye??

  • One Louder

Posted April 24, 2006 - 07:57 AM


0 to 1/4 throttle is affected by the fuel screw and the pilot jet. Have you cleaned the carb good? do you have an extended fuel screw? these are very touchy and the fuel screw will need frequent adjustments

BTW welcome to TT :thumbsup:

  • eddiev

Posted April 24, 2006 - 10:57 AM


I have a 99 also and I think spending time with the jetting helps a lot and I bolted on a part called a P38 from Factory R&D. It helped even more!!!

Good Luck!!

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  • ryan c

Posted April 25, 2006 - 10:55 PM


Clean yor accelerator pump on your carb its simple, and its your soulotion to yor problem

  • frig

Posted April 28, 2006 - 09:48 AM


Yes, cleaned carb, what is a P38 and where do yoou purchase

  • ben_suhard

Posted April 28, 2006 - 10:26 AM


I own a 1999 yzf 400 low hours looking for some info about low end carb hesitation or a dead spot int the
beginning of throttle

Even when the bike is jetted properly, you'll still get a bit of hesitation when opening the throttle quickly because with four-strokes, the engine doesn't produce as much vacuum as a two-stroke at low revs. One trick is to turn the idle up a bit so that the engine is creating more vacuum.

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