Question about tube that MJ screws into?

3 replies to this topic
  • CO_Rider

Posted July 13, 2007 - 11:41 PM


I have switched out my Main Jet on my 07 YZ450 twice now and both times the entire tube that the main jet screws into comes out with it (cant just screw out the MJ) Is this commen? I have a 05 YFZ450 and had a YZ250F (same carb I believe as the 07 YZ450?) and never had this happen. I am just curious if this is normal and also do you just screw it back in all the way? Like I said I have never had this happen before so I don't really want to be messing anything up in the carb.

  • bigred455

Posted July 15, 2007 - 12:18 PM


Very normal to have the nozzle come out with the main.Very simple solution,tighten the nozzle with 1/4 INCH ratchet.When you put the main in ,button it up with just your hand and a 6mm socket.Then just give the main a SLIGHT turn with the ratchet nothing more. Next time you drop the main,give it a quick turn to loosen and the nozzle will stay put.

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  • Racer24

Posted July 15, 2007 - 01:34 PM


thats the needle jet....the jet needle, when the throttle is closed sits all the way through it and you can sort of see it if you look into the drain plug..its normal...the main jet screws into it..and the needle jet screws into the carb...the main and needle circuit work hand in hand all the circuits overlap but the needle and main circuit control basically 1/2-wot

  • CO_Rider

Posted July 15, 2007 - 04:09 PM


Ok thanks guys. Like I said I have never seen that happen before and I probably have jetted the YFZ 30 times in the last 3 years. But thanks for the tips :thumbsup:

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