I had been out of the atv game for about a year but still had my raptor(was away at college) Now I am back from the summer I have been reading on here for hours in advance of my purchases and decided to start upgrading. (used to have a tricked out banshee—these four strokes are a lil more new to me) I got a full yoshi exhaust and today got my K&N clamp on running without the lid. I have 25 pilots—needles are 3 notches down from top.running 155 in the carb on the right (if your standing behind) and 150 in the left. These are yamaha (stock jets from the dealer….. I was going to get the dyna jet kit but wanted to be able to get what I needed from the dealer. TO THE PROBLEMŕ well getting a little frustrated because with trying to match similar people setups with mine it should be right on but it’s FAR FROM!! Its good half throttle in first and second but after that it bogs down the kinda starts of real quick. It also (when trying to accelerate past ˝ throttle throws some flames out ( I did take the sparky out) but the doesn’t seem right at all. Again when I down shift to decelerate. I also put a fresh plug in and tested this about 30 min ago so I could give you and accurate diagnosis. The plug color is not the tan that the old stocker was, its kinda a white color or Light gray.. (lean I thought??)

I also thought I adjusted the air screws to 2 ˝ turns out…there is and air screw on each carb kinda on the back—like if you remove to boot ..real small???

I tried to give you all the info I have…any ideas would be most appreciated…

 

if the plug is white/grey then you are lean. Ask yoshimura for jetting specs, they usually have that info available to customers.

 

I WISH..actually i called them today and the "tech" said that stock jetting is what they test with...... I asked him how that was possible and he kidna just didnt know what was going on.. saying his books didnt say anything about rejetting. I said thanks and goodbye...

 

Try 165mj left carb, 170mj right carb

 

I'm with Ernie better to be rich than lean . I dont know what your altitude is but here in Idaho on a raptor with opened exhaust and opened intake most run 170 left 175 right side fuel screws out 2 1/2 turns

 

My brother is running 150/155 DYNOJETS on his raptor with a e-series, no lid and foam filter..we are at sea level too. Remember that elevation affects jetting too!

When jetting, remember that dynojets and mikuni jets are different in sizes. You cannot compare mikunis with dynojets! So always ask if someone is refering to mikunis or dynos!

 

I agree with Ernie and maybe another 1/4 turn out on the mixture screws. You should also check and adjust the float level while your at it. Those are air jets in the back of the carb not screws, there's nothing to adjust there.

 

http://forums.atvconnection.com/mess...did/452930.cfm

160-165 sounds like a good starting point, i have 3 turns out on my screws, but i have stock pilots

 

For troubleshooting for lean or rich, (i think from your description, its lean), try putting the lid back on the air box, this will richen all ranges. If it improves, then youll know its too lean.


I know you said you did some reading, ...did you read this one on jetting. Its probably one of the better ones.

jetting

 

My raptor with a yosh and K&N proflow with outerwear runs good on 25 pilots and 165/170 with a hacked up lid. I was just up riding around 2500-3500' and i had to take the outerwear off cuz i was to rich.