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Twin chamber forks, bought heavier springs, educate/valving/mods needed?

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I have made valving changes on open chamber forks and feel very comfortable working/diagnosing those thanks to the folks here. Thank you!

Now I am working on a set of twin chamber KAYABAS for my buddy on a 2012 WR450. My riding bro is a bigger guy 6'4" 275 and we ended up with a set of .50s in the front and a 6.7 on the shock based on a call to factory connection and some internet research. think this is going to be a good set up for him, an older/slower trail rider. With the added stored energy in the springs (up from .46 /5.5 stock).. I was going to possibly add a couple shims to the rebound stacks to make sure he wasn't going to get bucked and it track straight (Feel free to opine on this as I am not yet totally committed to this idea). but I am lost on the forks and now that I am in there.. I am thinking why not do whatever else I can to make it better...

Can someone please break down the forks and where the changes get made.  a cliff note version Twin chamber 101 please? major parts and their function over the stroke? the "the base" valve for these is actually the portion of the cap below the compression springs? does it function the same way as the base valve on OC forks? the base valve stack on these is a single stage stack I didn't write all the shims down but it is pretty straight forward, should I think if pulling some face shims and adding a cross over like I have done on the OC mx forks revalved for trail work? Also I forgot to tell him to buy stiffer compression springs, is this going to be a major issue? inside the cartridge, this is the "mid valve"? compression stack on the bottom rebound on top? I disassembled those and wrote down the stacks but don't have them in front of me. after reading a little on race tech it seems like this is where most of the valving changes get made?? My thoughts after riding his bike before the spring change: seem like the forks lack plushness, bottoming resistance is good, maybe too good. mid stroke doesn't seem very progressive, damping ramps up quickly. I am 75lbs less than he is tho.. 

I am open to suggestion as far as valve stacks  oil heights (thinking of going with the least amount of oil) or any other mods that I can do to make these forks/shock better while I am in there. thanks to all for contributing. you folks and the info on here are what make this place a wealth of knowledge for noobs like me.  

2-twin-chamber-fork.png

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I put a Midvale eliminator on mine, made a huge difference in moto. Not sure if that's right or not for your buddy

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