I HAVE A 1995 CLARK CGP25 WITH A 4 CYL MITSUBUSHI PROPANE ENGINE WITH A PROBLEM WE CAN NOT FIGURE OUT.WHEN FIRST STARTED ALL IS FINE BUT WITHIN MINUTES OF RUNNING AT HIGHER RPM UNIT BEGINS TO RUN ROUGH AND RPM'S SLOWLY DROP TO THE POINT WHERE IT STALLS.IF HELD TO THE FLOOR WE GET SOME BACKFIRING THROUGH INTAKE BEFORE IT STALLS.IF WE LET IT SIT FOR A MINUTE UNIT WILL START AGAIN BUT SEEMS TO HAVE NO COMPRESSION WHEN YOU FIRST CRANK AND THEN STARTS AFTER 10-15 SECONDS OF CRANKING.IGNITION SYSTEM ALL CHECKS OUT FINE.ANY IDEAS