[yfz450racer]

i jetting my 450 with a 180 main and a 45 pilot jet and put 2 1/2 turns on my air screw
i took the air box lid off and the baffel out but and its buring good and but when i jam the throttel fast it pukes and if i just ride normel its fine but just when i jam it quick its quites please help me

 

[edgerat]

something you are going to have to get used to on these things is that they have a big carb on them and they dont like a shitload of fuel off idle. Try raising the idle 10clicks and see if that helps it. If not you just have to learn to have a little different throttle control.
Isaac

 

[yfz450racer]

ok thanks just needed a little info

 

[edgerat]

w e r d 8)

 

[killerkx327]

if the only things you've done is remove the airbox lid and baffle. then you're jetting it way to rich.
try a 160 main,42 pilot,2 1/2 turns out on the fuel screw and lower the clip on your needle one slot.
and something that will help tremendously is to get yourself a CNVQ needle.its the same needle the yz450 bike uses. the stock YFZ needle is way to lean after mods are done.
and another thing, you will not get real good off idle throttle response froma four stroke like you can a 2 stroke. there isn't enough manifold pressure to introduce the fresh fuel/air mix like a reed valve motor, it has to go thru the valves first.
as long as you don't have a huge bod a stuuter when you're under a load then you'll be fine.