Which big bore kit

[coachhejl]

Looking to go 70cc/47mm BBK in my 4 stroke.

Do I need to replace cam with bette rone? And do I need a new valve head if I'm using same size valves?

If I just upgraded the size of the piston and obviously the cylinder...but kept everything stock...how much of acceleration and speed upgrade would that provide if it was able to jet and tune the carb accordingly?

Just need to know if I need to get new cam and if I also need a new head.

I see some kits fairly cheap.

Cvt and variator upgrade would be next.

[aeroxbud]

[br4inl3ss]

stock cam works fine. a cam is an upgrade not a must do.
be sure the kit doesnt have a dome pisto. if its a dish piston with matchign head ( to run a decent comrpession ) then you should be good for a season or two. unless you already replaced the FACTORY crank.

speed gain is impossible to tell. some gained no top speed at all ( maxed out from gearing ) some gained 15 km/h.... depend on too many factors. BUT acceleration is another world. its like comparing a civic ( even modded ) to somethign that actualyl make some power... like a toyota prius maybe ? lol. the acceleration gain is massive.