i hear about 36,37mm replacements do they makle that much differance.
You are probably referring to .36 and/or .37s?? That would be a kg/mm measurement.
Would depend on riding style and such..but at 200#, you wouldn't be using something that small. .42s maybe. That would be in the 'woods/trail' mode.
If by 'jumps' you are referring to MX type stuff, then I know a very good MX KX rider that's a lightweight (like 140# soaking wet, likely) and runs .50s.
But then...a KDX is going to need a lot more the heavier springs to run MX.
imo.........
It's a combination of valving AND springs that will make the difference. With a complete setup (front and back) the difference is HUGE!