It depends if it's k-jet or the later electronic injection system that's on it (1.8 KR or a 2.0 ABF).
If it's k-jet (KR) the mixture can be adjusted via a 3mm (iirc) Allen key on the metering head on top of the airbox, clockwise for richer and anti clockwise to lean it out.
I would take it to a specialist though as k-jet is tricky to get spot on. Another reason I ran twin 45s on all my KRs.