lower a bike with suspension

[yz250falex]

I recently bought a yz250f 2003 and I feel that the bike is kinda low.

I would like to know if there's a way to lower the bike only with revalving or if the previous owner change the suspension or the spring...

I wonder if i can just revalve to make it a little bit higher

(I compared mine to my friend's and mine is really a little bit lower)

Thx for answer

Alex