I had a similar problem with my 98 scrambler 400 4x4. If your float height checks out alright, check the brass tube in which the needle slides in and out of. The small pin that holds it in place had slid out on mine and caused it to rotate 180degrees. When I would open the throttle it wouldn't let the correct amount of fuel into the intake. The cutout on the brass tube should face towards the reeds in your engine. Hope this helps.