i am putting a dynojet kit in my 99 400ex and have some questions. first of all the stock main jet is a 148 and the jet in the dynojet kit says to run a 142. what is everyone else running. i also have a white brothers e- series pro meg exhaust system on it and a k&n filter. second of all when taking out the stock main jet do you have to take out the adapter to put the new one on or not. it isn't detailed out very well in the instructions.the jets that came with the jet kit are 134, 138, 142, 146, 155, 160, 165, and 170. Any help is greatly appreciated.

 

i'm running a 160 main jet with a big gun exhaust system and a k/n with no airox lid right now....one thing you need to consider is your elevation because that makes a difference...i run at about 3200 ft and this setup seems pretty good

 

ok i put the 160 in and no change it still stalls when you open the throttle all the way.it don't even feel like it made any difference. do i have to move the needle(it's on the third position) or the fuel mixture screw(3.5 turns out).i'm starting to get ticked.

 

fast400,
im kind of in the same zone your in i was running a stroker slip on,155 main with 10 filtered vents.depending where you are in OH,im in northern KY. remember though to always step up on your mains until it cuts out at w.o.t.then step down once on your main jet,then that should do it.

 

where does the needle come st on the stock machine (400 ex) i have jet kit with a yosh,rs3 the bike felt better stock cant remember where the needle was from the factory want it to be all stock again its just to loud especially for night riding in va.

 

i have a lrd full exhaust k&n filter and no air box lid, and im running my neddle on the 4th notch down as apossed to the stock 3rd.i have the stock pilot jet and am running a 170 main, and i think the bike flies its faster then my freinds 400 with his white bros exhaust.i dont know what my elevation is but i live in nj.FAST400 said that you were stalling at full throttle????????if so it sounds like your running too rich.did you do a plug check??run your quad at full throttle then pull in your clutch and shut it down, pull your plug and see what it looks like, white is lean and black is rich, golden brown is perfect.hope this helps out.
quad040

 

forget what everyone else tells you (no effence to everyone else) start with the biggest one you got (170) run it up the road/field wide open about 200-500ft turn around come back wide open just before you get to the shop pull in the clutch and cut the motor and coast in take a plug reading if it is a dark tan stay with it, if it is a white/light brown color your still lean go up to a 175 or 180. If it is black go down to a 165 try that. the bast thing you can do is not ge discuraged, I work in an atv shop it has taken us all day to jet some bikes. The only time a bike is jetted the same is when it comes out of the factory. It often isn't jetted right then. Running to lean will flat ruin an engine running rich won't hur't it. It will only foul plugs and push black smoke out of the exhaust when you hammer it. (Don't jet it backwards)

 

ok now i'm really getting ticked. my riding buddy has exact same mods and put his dynojet kit in and used the 142 and his runs like a rape ape. i'll have to put my axle back in and try the 142 and go from there.

 

fast400
You should be able to run the pilot adj. screw and the needle right where K&N say with a 172 Keihin main jet,no airbox lid. There is no way your buddy's bike should be faster. Been there done that!!