Help my Sons Scambler 90 is a dog! Slow need help

Ok guys here is my problem I took off the speed restricters one was on the carb. and one was on the cluctch. This thing is a dog. problem.
slow take off . Was at Tower City yesterday. It appear to run great for a while. we then went thur some water seem to slow the thing way down. He could not climb hills. Need more takeoff power and overall more speed.
How do you adjust a automatic to run faster
thanks

[400exJOE]

HOW ABOUT A D&D PIPE???

http://www.atvsource.com/articles/product_reviews/101901_d_and_d_scramble_pipe.htm

I think this should help out if you're willing to pay for it. They seemed pretty satisfied with it too me.