I did a few things to my 300ex over the winter, and I need some carb tuning advice. Here's what I did...Arias +2mm piston, Web"bolt in" cam, wholy airbox lid, WB E-series, 38mm DG Keihen round slide carb, 350x air boot, K&N. The bike runs stronger and it is now almost even with my neighbors 400ex (he use to smoke me bad), but it doesn't feel as fast as the 400 when you ride it. Do I need to move the needle up or down? It doesn't hesitate or backfire. I was just trying to get a bit more throttle response,if that makes any sense.

 

You can move the needle up one notch and that will richen the mixture from about 1/2 throttle upwards. Moving up the needle pulls it out of the orifice allowing more fuel flow. You should 'read' the spark plug often to see if you have it too rich. It should have a light to dark brown color to it. If it is too rich, it will be black with soot on it.