Front shocks i am guessing, there are things you can do, like spacers in the top, heavier fork oil, and if they are link my ProX250 there is a air nozzle under the rubber gromit on the bottom of each fork, but after all that it doesnt make a huge difference only a little, i have done it
The only real way is pull the forks apart and find a company that makes springs and get heavier springs made about $100 - $140