another jetting question.....

4 replies to this topic
  • sjw

Posted June 13, 2003 - 07:52 AM


ok...wr450 stock jetting,all mods done.heres my question.I put a fmf Q exhaust on it runs fine then I get on
the fmf web site and it says main 178 pilot 42 clip in the fourth do they know what I need?
what elevation or even where I live? whats up with that ? should I try it ?

  • Machster

Posted June 13, 2003 - 11:31 AM


I called FMF being that I have the same pipe and same mods..they told me 180 main 42 pilot Stock needle on clip 4, 1 3/4 turns on the air screw with all the free mods at sea level to 2k ft. Now this goes beyond all logic. I asked about the yz, and was told it was 178 42 stock needle clip 4. sooooo where do we go from here. It sounds like they are just throwing gas on the problem. Should be interesting to try at least huh?? :)

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  • captain_S

Posted June 13, 2003 - 12:10 PM


How do they know what you need,they dont!,i guess they are doing what yamaha have done and are giving the wr heavy jetting(on the conservitive side)working on the hope that some riders dont ask for all the motor can give,and hope they will never notice!,i dont think this is a good idea as it can do a motor as much harm as having it too lean(the smoother it runs the more trouble free it will become),i dont know about the 450 with standard timing and jetting,but on my 426 with yz timing just sticking in bigger jets is not where its at,it`s how you meter the gas flow that really counts!,sure the Q pipe will let the exhaust gas flow out a little better but be wary of just sticking in bigger jets just for the sake of it! :)

  • Machster

Posted June 13, 2003 - 12:56 PM


Ok..for the heck of it, I tried this setting 178 42 1 3/4 stock needle 4th clip...and believe it or not, my bike actually is running better. Started first kick crisp all the way through the powerband. I know this sounds weird, and believe me, it is. The only thing I can figure is the new carb is so much different than the 02's that it may need more fuel to run properly. Until we figure out what to do with the maj, this might be the ticket. Someone else should try this to back my findings up(if you have an fmf q series pipe) :) :D

  • Indy_WR450

Posted June 13, 2003 - 03:38 PM


How black are your plugs with a 180 main? This seems way off. I have noticed that the 03 carbs seem to work better with smaller mains due to the larger MAJ. I would like to know how much jump in main you had to go to get it to work.


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