There is a "Suspension" part of the forum , just so you know , but it would most likely be me replying for the most part
https://www.crfsonly.com/forum/viewforum.php?f=36
With that said...
I have never heard of them seizing , are you sure they were not over adjusted either in or out too far ??? , as i am assuming you are not the original owner and you bought it this way , but , they have had to have been severely over tightened to have the screwdriver slot strip out and to have them not be able to be moved , i have never heard of it happening before , and most likely if they were overtightened then the adjuster needle is toast and it will not adjust anymore anyway and will need replacement
I just now looked up the parts and......
Part# 14 is on the list , but # 35 , looks to be no longer available , and BOTH are the 2 parts you need , as each is different , so it looks like buying a new set is not a option
http://fiche.worldofpowersports.com/yel ... 0-%20FRONT
As far as how to adjust them , well , about the only way if they won't budge is to remove the cartridge and take the compression needle out and first see if its damaged , if its even very slightly compromised , it will have to be replaced , there is no "fixing" it , if your not experienced with tearing the fork cartridge apart , it might be too much for you to mess with , as it is very involved to get the needle out , if you question your ability to tear it down as far as you will need to , which is far more involved than replacing fork seals , and falls more along the lines of revalving , but even a bit more involved , then , your easiest fix would be to find a used set of Fork Cap Assemblies or Cartridges or a complete used set of forks
If you think you can do the work , i can walk you thru it , but , you will still need to find a replacement needle or Fork Cap Assembly or Cartridges for both forks , and usually the only way to get them unless you happen to find some in a suspension shop , is to find some on eBay , again , if your mechanical skills are not decent and you have not been into the forks a few times , (they need to be a set made for your year/model , left and right are different according to the parts fiche) then you need to find a complete used set of forks , there really is no other way to "fix" this issue , replacement of some sort is the ONLY option at this point
You might be better off hitting up a suspension shop and see if they have any stock Fork Cap Assemblies or Cartridges laying around they might let go for cheap , or hitting eBay , as getting them new is out , so , you could probably find a complete set of forks on eBay and be better off , as you could probably find a pair of forks for about $150-$300 (closer to $250) depending on the condition , and stick them on and ride for the season , then in the winter , change the fork oil and maybe the fork seals and your ready for next season , and , you will be able to adjust them ... I feel bad for you , as any solution will not be cheap .....Unfortunately , there is no other way to get functionality back because i will guarantee the needle is ruined as they are very delicate and any over tightening will easily render it useless as you have found out .....
