Breaking Up

[YFZ450 Racer88]

I have the full TC Exhaust on my 450 and when I get in the top end or higher RPM's it starts to break up bad!!

Main jet is 162
Pilot jet is 42
Air Fuel screw is 3 1/2 full turns out
Clip is 2nd Notch from botom on STOCK needle
Did not get Bike needle for it?? Should i , would this eliminate the prob???
Stock intake and filter
Plug is light Brown so its not running to lean
5th gear it also will cut out when ur 1/2 throttle going pretty fast!
Please would liek to know if it would be better to have a dealer rejet it and test it on their computers. Or for me to just ajust something!!!!!!!!!!!!!

Thanks

[Bill Fuller]

Do you have the air box lid on?I would suggest going to a 45 pilot.When you say the needle is on the 2nd clip from the bottom are you saying from the blunt end or the taper end?I would suggest going to the 5th clip on the stock needle(toward taper/richer).I would also try a 165 main.The only way to learn how to jet is to try try again,you'll get it.If it's in the upper RPMs than it's most likely the main.

[YFZ450 Racer88]

Hey thanks alot dave
I will try this and see if it helps
i have the clip at the second slot from the taper end
and i think im gonna try a 165 and a 45 which was suggested to me at the track!
But wasnt sure
thanks se how everythign goes

[Bill Fuller]

Dave:confused: