If you have a intake manifold for a 44 Mikuni carb then yes there is an adapter available actually two choices.
#1 converts the Mikuni intake to a Keihin intake bolt set up and will allow you to install a 38 or 42 Keihin CDKII carb standing straight up. The issue when i used a 42 was it hit the cylinder so I had to use option #2
Option#2 same idea but this time the adapter tilts the carb away from the cylinder at an angle to it clears.
Personally I entended up using option #1 and then buying a intake spacer and spaced the intake setup away from the clylinder and it workes awesome.
Heres a pic of my intake setup - wont see this on many skis.
Under the carb is a black adapter option #1
goto hotproductsusa.com and download the catalog page 20
to order parts try John Zigler at Rock County, John at Jet Ski Haven or Dale at Dales Jet Sports they all are dealers.