Yz250 jetting/carb problem

[johnnyl]

Hi got a yz250 03 dep pipe vforce. The stock jetting here in the UK is 52 pilot n3ew needle 3rd slot 180 main. The problem is that the pilot circuit seems very rich, have to keep hard on the throttle to stop plugs from fouling. I have dropped the pilot jet down to 48 then 45 this has made some improvement, not fouling plugs anymore although it still seems too rich. The thing is the smaller jet cleans up the pilot circuit but at the expense of performance loss at the top end of the pilot circuit going into the needle. I am thinking of raising the needle 1 slot to richen the overlap between pilot and needle throttle positions. My concern is that the jetting is getting way off stock and that I may be overlooking something.
The crank seals are good, new top end.
Anyone any experience jetting YZs or any ideas?

 

[rbn14]

On my 05 I had to go all the way to a 42 pilot to get it real crisp(with an fmf fatty). Since then I have gone to a JD jetting kit, which I have been quite impressed with. The kit comes with two needles that may solve your problems.

 

[oldfrt613]

I am thinking of raising the needle 1 slot to richen the overlap between pilot and needle throttle positions. My concern is that the jetting is getting way off stock

These changes do not constitute "way off stock". We also have dropped the needle and leaned the pilot circuit down to improve our '04 and '05.

 

[BSWIFT]

My 05 YZ now has a 45/175. I was going thru plugs like crazy. I'm a bit lean on top and will be raising the needle from the mid clip to the second from the bottom to richen up a bit. Air screw is 1 3/4 turns out. The bike is very crisp and is a handful if you don't control your wrist.
BTW, I'm at 700' above sea level and running stock pipe and silencer with no other mods.

 

[johnnyl]

Thanks for the replies, feel happier now experimenting with the jetting. I will post back later with results.