LJ55 ENCOUNTER TEMP INVERSION AT FL430 IN ZNY AIRSPACE ENRTE TO BERMUDA; ATTEMPT DSCNT CLRNC WITH COMRDO AND ZNY; BUT DSND TO FL425 UNTIL FUEL BURNOFF ALLOWED CLB BACK TO FL430.

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ZNY ATC TOLD US THAT WE HAD TO BE LEVELED OFF AT FL430 BY RETTA INTXN; WHICH WE DID MAKE; BUT THE TEMP OF THE ATMOSPHERE WAS INCREASING WHICH WAS NOTED; AND THE INCREASE IN TEMP PREVENTED US FROM MAINTAINING FL430. SO I MADE THE DECISION TO DECREASE ALT TO FL425 WHICH THE ACFT WAS ABLE TO DO. AS TIME WENT ON AND THE ACFT BECAME LIGHTER AND LIGHTER FROM THE FUEL BEING BURNED; WE WENT BACK UP TO FL430; WHICH WAS ABOUT 25 MINS AFTER WE INITIALLY DSNDED TO FL425. WE TRIED TO GET A CALL ON FREQ 8846 KILOHERTZ; BUT THE STATIC WAS SO BAD; I AM NOT SURE THE CTLR EVEN HEARD US. WE ALSO TRIED THE BACKUP FREQ OF 11330 KILOHERTZ AND VHF 129.90; BUT NOTHING. WE WERE IN VFR CONDITIONS THE ENTIRE TIME AND WERE LOOKING FOR OTHER ACFT. THE FACT THAT THE TEMP WAS HIGHER THAN I CAME UP WITH ON THE PREFLT PLANNING WAS THE REASON THE LOSS OF PERFORMANCE OF THE ACFT. MY OPTIONS WERE VERY LIMITED. I COULDN'T HOLD ALT. I DIDN'T WANT TO MAKE ANY TURNS; AND I DID MAKE SURE I STAYED OUT OF RVSM AIRSPACE. MY DECISION WAS TO TRY 100 FT INCREMENTS OF LOWER ALT AND WE HELD ALT AT FL425. THE ZNY CTLRS DID INFORM US THEY MOVED ACFT OUT OF OUR WAY WHEN THEY SAW US DSNDING LATER ON WHEN WE TALKED TO THEM ON 128.50 GOING INTO BERMUDA.