Replaced the main jet and I still hesitate taking off. I'm sure I need to dial in the air/fuel mix screw, it's starting to get frustrating. Checked the valves and gave the thing a tick, going back in to it when I have time Sunday. http://www.amazon.com/gp/product/B003CJIJ0E the 100 is what I bought, and it seems to be more responsive over 15mph.