I just installed a new Athena 144 kit on my 01 YZ125. The jets I took out are 22.5 pilot, and 450 main. I installed a 35 pilot and a 480 main. The motor stumbles before it hits power band and in beginning of power band. I expected some drop off on the top end, but I'm dissapointed with the bottom and midrange. I'm hoping its a carb issue. Any help would be appreciated. The weather has been between 50-60 degrees when riding. Also using 50/50 mix of U4.4 and 93 octane (98-99octane) with yamalube 2R.