Mine did the same thing, same direction (left) until I checked the fork height in the triple clamp. The right side was just slightly lower than the left. I made them even and it helped a lot, though still not quite right. Could be the brake caliper dragging on the left side.
Aftermarket windscreen? Mine did/does the same thing and after exhaustive tinkering by my local stealer, checking triple clamps, wheel bearings, steering head bearing, brakes etc... they couldn't find anything causing it, but did agree it pulled to the left. I switched back to my stock windscreen and problem pretty much went away.
Loaded unevenly? Carry stuff in one side case and not the other?
One brake caliper dragging will not steer the bike!!!! Perhaps you've seen those more primitive conveyances with only a single disc at the front? Are you gonna tell me those guys have to steer against the brakes every time they use them??!!??! Hell, no wonder they don't like using the front brake!!!
Mine wants veer left also, my road king did the same thing. harley riders maintained it was because of all the final drive shtuff was on the left. Probably the same with the FJR.
Tightening the axles and pinch-bolts in improper sequence can cause this problem. A free thing to check is to loosen and re-torque both axles in the proper sequence. Worked for my bike. It tracks straight with no input for miles and miles.
If you are on a paved road with a slight crown, like most are designed, your tires are riding slightly left-of-center, so it us just like you leaning to the left, and you go left.
Also, sometimes for fun I try to see if Sally and I can balance on the seat well enough to keep the bike straight without gripping the bars. Sometimes when we manage to get it straight Sally says she feels like she is hanging off a little.
So, its a little off-center weight and a little tippy road....
A few years ago there was a poll in this forum on the subject of the FJR pulling to the left with no hands on the bars. The result was that almost all of them do; those that do not are few and far between. I had a tech from Olins Shocks tell me they all move to the left and he thought it had to do with the drive shaft on the left.
I just put a new front tire on my 2007 and it seems to pull less. So I believe there is something to the theory of crowned roads wearing the left side of the front tire and with wear on the front tire, I expect more pull to the left.