Parts for XR-70

Aug 20, 2003
Ok i was looking at fixing up my sons XR-70 to go faster and i was looking at a Takegawa Hyper CDI Box saying it will let the engine rez past 12,000 rpm and a stronger spark, anyone have any exp. with this item. Second, item is front and rear sprockets and my question on that is if i change them out with different teeth will i have to change the chain out with it or will the stock chian still match up and can i miss match the front and back sprocket for more take off and less top end or does it hurt to miss match. Please Help going to buy for christmas. THANKS ALOT.