Recently picked up a 2000 400ex. It had a knock off carb on it so I replaced it with an oem one. The issue I’m facing is when I’m at a low idle speed and punch the throttle it’ll bog down for a second or 2 and then take off. If I ease into the throttle it runs perfect. The 400 is all stock, i just recently added a fuel filter, changed the jets to 148/38, and added a new spark plug.