You can measure the lengths from the axle to the top and compare, then subtract the RS forks from the stock ones, and follow the settings recommended from the NSR-World tuning pages.
If your triples are modified or not stock, then you need to see if they are lower than the stock ... if they are a different offset from the axis of the steering stem then you're going to have to do some more involved geometry calculations.
I've got the old RS250 front end (non-USD) and it is frighteningly shorter. I am going to set it 5mm recessed into the top triple clamp (I.e. -5mm showing) and I'm still going to be 8-9mm shorter than the HRC settings still.
I'm still waiting on somebody pointing me to some frame geometry measurements so that I can make a rake and trail calculator.
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MC28 SE -sold-
MC21 with RS250 engine -for sale-
MC21 race bike -soon for sale-
