My kid's T-rex piston and rings went last year so I decided to hop it up in the process. So I got a ported cylinder, carb, manifold, exhaust, air filter, clutch, head, and of course piston and rings. At first the thing had no bottom absolutely none and the bike wouldn't start really get going until about 30 sec of full throttle. Then I called my vendor of parts and mentioned I needed a transkit. I got the transkit and the power came on sooner but the bike still doesn't have the 4 stroke responsiveness torque it first has. Don't get me wrong, this thing is a screamer and when the RPMs come up it hauls @ss. However it's for my kid, and he isn't a WOT throttle rider he is more of recreational rider that would prefer more bottom. What can I do to bring more bottom end to this? Different exhaust? Stroke it? Different variators? Need some advice/help. Thanks in advance to anyone who answers.