05 900 RMK no rpm read out

the RPM is read by a crank position sensor (CPS) on the flywheel connected to the stator wiring harness..

from the ECU plug #1 to the gauges, its a YELLOW/RED wire...you can try check that first to see if its frayed/broken..

if its not the wire from ECU to hood...check wiring from stator to ECU and see if its frayed/broken or if the pick up is bad..the RED/RED-WHITE wire from stator wiring

OR...........you might have moved the CPS (2 tooth) when you removed the flywheel/stator and when you installed it, the GAP from the pickup to crank is not set correctly.."BOTH CRANK POSITION SENSORS WILL HAVE A GAP TO THE FLYWHEEL OF .035" or (.90MM)"

HOPE THAT HELPS GET YOU STARTED

Well, if it was Crank pos. sensor related that motor wouldn't run at all, it's kind of the first question asked by the ecu that must be answered before anything else can happen. Since you indicated it is running fine other than tach, then try tracing the tach pulse wire from guage pack (yellow/red) down to your chassis hood connection and see what you find. Keep us posted!