forget what you where just told, heres the real deal....
okay first of all i know for certain for a 200lbs rider we need a 14.3kg/mm spring. the stock fz1 on the pre-06 models is a 12.5kg/mm spring. so the shock is sprung right for the bike and will dampen properly with a spring up to about 15.5kg/mm (which you can buy off a honda, their stock springs are really heavy too so no need to buy a racetech just buy a used honda 929/954 shock for its spring. the whole shock wont work though as the base wont hook up with the fz swing arm). the new ones (06-08) only have rebound adjustment where the older ones have compression too. the thing is the older ones are about 7.5mm longer, or at least they have .3" more stroke. BUT the 00-05 shock has a u-type fitting at the bottom that can be easily cut and re-welded if it doesnt bolt up and you can shave off the extra length. the 06-08 should be the exact length but like i said have only rebound adjustment. for track riding having a longer shock will be a good thing, it does about the same thing as lowering the forks through the tripples. i havent actually measured the real overall length of the shock though but it looks to be the best fit, if anything you could settle for the not as good new model shock though if you cant weld.
heres why an r1 shock wont work; it comes with an 8.8kg spring, we need something like 13-14kg range. BUT you cant just buy a new spring for it. when you put on a much stiffer spring, a generic stock shock doesnt have the headroom in the valving to dampen that spring and will have to be re-built with new valves to make it work, but that'll run about $500 total to do. you will be worse off in the dampening department than you were before without a re-build.
also another alternative is to buy a penske, ohlins, elka etc for a bike that has close to the same length shock. you will then be able to simply swap springs and have it work right. because aftermarket shocks have about 4 times that valving headroom than a stock shock so you can play with drastically different spring weights.
i have researched extensively and talked with the pros about this. there are only three main components to a shock that are important for us on this.
1.length/stroke
2.spring weight
3.valving
r6 shock-doesnt work, too short and too weak
r1 shock-doesnt work, too weak
honda 929/954 shock-none bolt up, sprung perfect though, little short
kawasaki-too weak, dont bother
suzuki gsxr 1k- to weak dont bother
hayabusa-maybe, seems good but never looked further
fz1-best bet and will know for certain in a few days
