you should go to your Honda dealer and get the stock fork oil. as for making up for the lost oil, you could do it the right way and remove the fork from the bike and remove the preload spacer, washer and spring. fully compress the fork tube and fill the fork to 150mm from the top of the tube. reinsert the spring, washer and preload spacer. then tighten the 17mm fork bolt to 16 lbf-f.
OR if you only lost fluid in one tube and didn't mess with the other tube, you could try this.
get a friend to lift the front of the bike up so as to take all the pressure off the front forks. while the front is unloaded, undo the fork bolts. they will have a little tension on them from the spring but not much. after they have been removed set the bike down on the front wheel and keep the bike standing up straight. It is imperative that the bike be standing straight up or this won't work. remove the preload spacers and washers. don't remove the springs because you will lose the fluid that is on them and i don't know how much that will be. with a gauge of some sort. (i.e. a straight piece of wire or a wooden coffee stir stick) slide it into the fork with that hasn't lost fluid until it just touches the fork oil. mark it on the side of the gauge. then fill the low fork with fluid until the oil just touches the bottom of your gauge. if you pour too much in then you will need to remove some with a straw. now both forks should have the same amount of fluid in them. then reinstall the washers and preload spacers. get your friend to lift the front of the bike up and reinstall the 17mm fork bolts and torque to 16 lbf-ft.
if this doesn't make sense or you don't think you can do this easily then take the bike to the dealership and have them work on it.
here are some sites for caps and adjustable caps.
SATO RACING | Honda CBR250R ('11-) Fork Spring Preload Adjusters
CBR250R-EXHAUST
Steps and CNC Machined Parts - Tyga Performance
OR if you only lost fluid in one tube and didn't mess with the other tube, you could try this.
get a friend to lift the front of the bike up so as to take all the pressure off the front forks. while the front is unloaded, undo the fork bolts. they will have a little tension on them from the spring but not much. after they have been removed set the bike down on the front wheel and keep the bike standing up straight. It is imperative that the bike be standing straight up or this won't work. remove the preload spacers and washers. don't remove the springs because you will lose the fluid that is on them and i don't know how much that will be. with a gauge of some sort. (i.e. a straight piece of wire or a wooden coffee stir stick) slide it into the fork with that hasn't lost fluid until it just touches the fork oil. mark it on the side of the gauge. then fill the low fork with fluid until the oil just touches the bottom of your gauge. if you pour too much in then you will need to remove some with a straw. now both forks should have the same amount of fluid in them. then reinstall the washers and preload spacers. get your friend to lift the front of the bike up and reinstall the 17mm fork bolts and torque to 16 lbf-ft.
if this doesn't make sense or you don't think you can do this easily then take the bike to the dealership and have them work on it.
here are some sites for caps and adjustable caps.
SATO RACING | Honda CBR250R ('11-) Fork Spring Preload Adjusters
CBR250R-EXHAUST
Steps and CNC Machined Parts - Tyga Performance
