Under your particular circumstances (dual US/FI citizen w/ ease of
securing FI address), it would probably be much less hassle to
buy new or used in FI, re-sell at end of your ride.
You need to explore cost dynamics a bit more.
Go to BMW Finland/ Suomi website:
BMW Motorrad Suomi
click on "Käytetyt moottoripyörät" (Used Bikes)
Contact any of the listed dealers for more details, both in terms of
pricing/ taxes and FI paperwork details for registration/ insurance/ etc.
You can also get FI new bike prices on same website.
You may also find Finish websites for private owner used bike sales;
depending on Finland VAT rules, private owner sales may be cheaper
This also assumes you are willing/ intending to start--and end--your
6 month ride itinerary in Finland
Yes, you can sea or airfreight from US West or East Coast, but the
cost & hassle of that is likely to be relatively much higher than FI purchase/ re-sale, under your particular circumstances--assuming
you do not want/ intend to return the bike(s) to the US--even if the initial purchase
price of the bike(s) is likely to be higher in FI than US.
If you sea or airfreight a US-rego bike to EU, you can ride it as a "temporary"
import throughout the EU for 6-12 months, without paying EU permanent import taxes. "Temporary" imports of US-rego vehicles are supposed to
be returned to US (or re-exported from EU) at end of allowed temporary
import period; but the enforcement reality is that many US owners keep
US-rego bikes in Euro semi-permanently.
It also depends on your plan/ intention for the bike(s) at the end of your
6 month ride. Do you want to return/ have those bikes in US at the end
of the 6 months ? If so, DON'T buy a FI/ EU-spec bike, because there are
strictly enforced & expensive US DOT/ EPA rules about importing EU-spec bikes (back) to US. If your intention is to have those bike(s) back in the
US after a 6 mos EU ride, then buy in the US and plan to air/seafreight
There are many HUBB threads/ posts about these detailed options, including
sea/airfreight, and required temporary insurance for US-rego vehicles ridden
in the EU.