Best thing to do is to PM Stoic Bloke, and/or read his Heroes-Legend 2010 thread about how he fitted a KTM front end (off a 625/640 I recall) to the Tenere...

Bear in mind you really want to get the forks from a 640A/690 or 990 Adventure, rather than an EXC as the spring rates will be closer to what you need for a 180+Kg bike, or at least factor in getting the forks 'tuned' once you've built the bike up.

I'd also suggest going to OTR and simply buying their complete kit - it's not cheap of course, but is all brand new parts, has the correct springs and damping set-up already, and bolts on in a couple of hours... it also meets TUV homologation, which might also be a factor in Finland?

You can of course make anything fit with a bit of work, but when the WP fork kit is available off-the-shelf, or secondhand parts arguably the most widely available, it makes sense to use those, together with the associated wheel/hub/disc etc dimensions...

Have fun!

jx

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