Thats only the half of it, look at the pictures of the fuel bowl seat on the stock carb. It the same size as a 170 main jet while the Grizzly is much larger. I know that many people have run 190 to 200 main jet size in the stock carbs but the fuel bowl seat will only flow enough for a 170mj size, which means they will have a lean condition at WOT for long periods at a time.