hi there i have a 03 Rappy and I had full yosh exhaust.. and was running 150 155 jets @ coast
I just bought a ProflowK&N and upped my Jets to 160 165 .. and put in my aftermarket needles... Tha damn thing will not run right it pops and backfires and sometimes it runs great when im revving but then just like "siezes" up at idle
it idles fine for about 10 seconds or shorter then makes a horrible sound like when you stall or something
ive tryed everything with the damn needles moving clips etc.. putting stock ones back in it didnt even start when i did that soooo i need help please thanks

 

Maybe you bumped the floats when you changed the jets.Do a search on floats. Posted is a real easy way to check them with a piece of clear tubing. Are you using the lid on the air box?What are your mixture screws set at? They should be about 2 1/2 and 2 3/4 if you put in 25 pilots. Middle groove on the needles.

Does'nt sound like it but make sure it's not the rev limiter.

 

its not the rev limiter.. no lid on.... 25 pilots ...are those stock size?? i havnt changed pilots if those arent stock

 

I ran a Pro-Flow foam filter with the Yosh pipe all last year. It was a pain in the a$$ to get the jetting right. Here is what I came up with after trying everything from 150/155 to 175/180 jets.

Main jets at about 160/165. Maybe one step higher or lower depending on altitude and air temp. Needles on the 3rd clip position (middle). This is assuming you are using Mikuni jets and needles.

Stock pilots are 22.5 on the '01 and '02 rappy. I assume that '03 is the same. I haven't heard of any changes in the carb/engine for the '03. You may want to try 25 pilots. It worked on mine, but I also added a high flow aluminum airbox at the same time.

Your fuel mixture screws (on the bottom-front of the carb) should probably be between 2 and 3 turns out. Turn them in all the way, then count the turns out. Try the left (when sitting on it) screw at 2 1/4 and the right screw at 2 3/4. If it pops and farts on decelleration (cruising at high RPM, then let off the throttle), go 1/2 more turn OUT on each screw. If you cruise in 2nd gear, then let off the throttle and pull in the clutch at the same time, and the engine goes to a very low idle, turn the screws IN 1/2 turn each. Hopefully this will get you going!

RR1

 

good advice so far. What kind of aftermarket needles do you have? I had trouble using DJ needles with the stock jetss, never did get it right.

 

im usuing dyno jet needles... and i guess mikiuni jets... ill try the pilots my friend said that solved his problem ill keep you posted.