bike cutting out??

3 replies to this topic
  • jay yz-f

Posted May 21, 2007 - 01:32 PM


hi all, had my bike cut out twice yesterday under full load, it cut out very violently and back again very fast with a bang, im wondering if this is due to my jetting im currently running 165 main jet with the rest stock (07 450), i have an fmf power bomb header with powercore silencer temps here are roughly 15-20, i ride mostly sand and am resonalbly fast, also the plug is a touch white, if i have something worng could somebody please help as im not very bright when it comes to jetting!

I have also had 2 stator plates go aswell so im hopeing it not another one on the way! the bike does back fire on idle bit i asumed this was due to the slip type fit of the fmf pipe

Any help would be great


  • CaptainKnobby

Posted May 21, 2007 - 05:09 PM


Yea!.... sounds like you are lean! with the after market pipe you put on you will have to richen her up. Try staying with the 165 main and move up to a #48 pilot and check to see if the jet needle is in the #4 clip position. Iam not sure what stock clip position is for the 07 but check it and if its not put it in the #4 position and turn your fuel/air screw all the way in to start out with and start turning it out in 1/4 turns until the idle starts to drop or roughens which will be at about 2 and 3/4 turns out then turn it back in till the idle picks back up (smooths out if you will) should be at about 2 and 1/2 to 2 turns out. Try this and if it does not work let us know what happens and we will help you on it. With jetting its just trial and error.....>> you just got to keep an eye on the plug as you switch jet settings and listen to what the bike sounds like and how its performing. Just remember! its better to be a little rich than to be to lean.

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  • jay yz-f

Posted May 23, 2007 - 08:53 AM


rode today again but with my sotck exhaust system there were no misfire or cutting out ! when i took the fmf apart there was not a bit of packing to be seen so im hoping it was that causing the prob, just got to do my cluthc now which has started to slip!

  • grayracer513

Posted May 23, 2007 - 09:27 AM


Yea!.... sounds like you are lean! with the after market pipe you put on you will have to richen her up. ...

This is not necessarily true. A lot of after market pipes will require no jetting changes at all, and a good number of them, typically the ones with larger than stock core diameters, will make the engine run rich.

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