Having small problem tuning

yfz 450. this is what is going on.  this happens in neutral and or in gear.  with a slow throttle roll, at about 1/4 throttle the rpms take off.  I cant get a nice slow smooth increase in rpms.  I played with pilot 45-48 no difference and am using dyno jet needle about 4 down. . about two turns out on fuel screw.  lid off. works fine if I punch throttle, just has this wierd spot I cant smooth out.  any suggestions appreciated  

are you saying the throttle revs high at a certain point?

if so check needle make sure it isn't worn or bent.

give any extra inform on it that you can  
Keep it RUBBER SIDE DOWN!!

yeah all of the sudden it takes off.  I cant get a smooth slow roll rev. it doesnt get stuck or anything, it just all of the sudden goes.  

does it quit as soon as you left off the throttle?
or stay revved for a few seconds after you let off the throttle?


could be just a matter of adjusting the fuel/air mixture  
Keep it RUBBER SIDE DOWN!!

no it comes right back off no poping or backfire.  

popping or backfire is a sign that it is too lean.
(not getting enough fuel)

so what it sounds like is that it is getting too much fuel.

try this:
mark where the fuel/air mixture screw is setting now.

then in 1/4 turns turn it to the right (in) 1/4 turn at a time. let it run for a few minutes then if no change then try another 1/4 turn. keep up with how many 1/4 turns you make so you can take it back to where it was originally.

if it gets worse then turn it back to where it was marked when you started and try turning to the left in 1/4 turns.

it really sounds like the fuel mixture is off.  
Keep it RUBBER SIDE DOWN!!

You are right dude thanks a lot.  

No problem glad to help!!!

if you get a chance check out the atvrider magazine.

it's definately worth the money.  
Keep it RUBBER SIDE DOWN!!