300ex bogs down at 3/4 to full throttle

Alright geez please help me here im going crazy here. My 300ex has just recently sputterin at 3/4 to full throttle it has always acted up since I put a 400ex carb on it and I am running a 155 main jet its like when Im hittin top end it starts sputtering and wont stop unless I let off the throttle its like it isnt gettin enough gas or something is clogged but its all clean. I was tryin to see if its jetted right today but had no luck I accidently put a 160 in and it seemed to not sputter as much but it just seams like a 300ex with fmf full exhuast no airbox lid and a k&n filter also to 400ex carb to be running anything over a 155 main please help me guyz:confused:

I know you said it seemed better with a bigger jet but from what you described it sounds rich...I'd go down a main.

Alright before today it had a 48 in it and it ran like it does now and it now has a 55 in it im gettin very frustrated with this. I can pay 50 bucks do have it done by a machanic or get some help by u guyz which i would prefer so hopefully i can get this thing solved

All 300ex owners with 400ex carbs please tell me what you are running for jetting

it sounds to me like you are describing a rich mixture...what color is your spark plug?

if it is black, keep going down main jet sizes ( I assume you meant 155 and 148) > i would keep going down until it stops sputtering.

when it was at the 148 it was gray

You may want to check you jet needle setting, usually is set on the 3rd gap. The lower the setting the richer it will burn. if you are in fact burning rich, try setting your needle up one notch. You could also be not getting enough fuel at 3/4 to full throttle and that to will give you a bogging (fuel starving) symptom. Then you may want to check you float level. Clean your airfilter and then run with your airbox lid off and then with you lid on. If it runs better with lid off then your rich. If better with lid on then your lean. This should get you started in the right direction.;)

that main jet is way too big for your 300, my buddy has a 400ex carb on his 250x(came that way) we took the jet out to see what size. it had a 122 in it, and that ran great. we are putting it on his 300ex, and we put a 130 in it. you are using a jet way too big for your quad. do you have a pipe or anything on there?

yea I have a fmf full exhuast

Alright, try a 130, or 135 main jet and clean the carb while your at it