Will the carbs off an '88 FJ1200 fit a '92? Any difference in jetting?
They should bolt right on. Might want to sync them once on the new bike. Carbs for earlier years are gravity fed and would need a parts changed over.
Here in the USA the 1988 FJ was not imported, however from others on this international forum I understand the 1988 FJ1200 was a fuel pump version...if so, then the carbs should fit just fine on the 1992 fuel pump FJ.
Jetting...? I have no clue....probably very close assuming both bikes came from the same region.
We know the USA bikes were jetted leaner than the EU bikes.
Jets are cheap, start with fresh new oem Mikuni jets, that way you'll know exactly what you have.