FLC OF A LEAR JET LR31 TOOK OFF ON A RWY OTHER THAN THE PLANNED RWY AT AN UNCTLED ARPT; YSN. THE RWY WAS SHORTER THAN REQUIRED BUT WAS SUFFICIENT FOR THE LIGHT LOAD OF THE ACFT. AFTER RECOGNIZING THEIR ERROR; THEY DECIDED TO CONTINUE THE TKOF SINCE IT APPEARED DIFFICULT TO ABORT WITHIN THE REMAINING RWY.

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OUR ACFT HAD BEEN GNDED IN CYSN FOR 2 DAYS FOR MAINT. WE HAD CANCELED 1 TRIP AND WERE VERY CLOSE TO CANCELING ANOTHER; BUT IT FINALLY CAME UP. WE PREPPED FOR DEP AS NORMAL; EXCEPT THE SIC DID NOT GET THE IFR CLRNC PRIOR TO STARTUP. AS THE PNF; I WAS SEATED IN THE R SEAT AND COPIED THE CLRNC FROM CYSN RADIO ON THE TAXI. WE TAXIED TO WHAT WE THOUGHT WAS THE HOLD SHORT LINE FOR RWY 6 AND HELD THERE WHILE WE SORTED OUT THE CLRNC AND PROGRAMMED THE FMS. CYSN RADIO RELEASED US FOR TKOF AT OUR DISCRETION (CYSN IS UNCTLED). WE TAXIED ONTO RWY 1; SELF ANNOUNCED A RWY 6 DEP AND STARTED THE ROLL. AT ABOUT 100 KTS WE BOTH REALIZED OUR MISTAKE AND CHOSE TO CONTINUE WHAT TURNED OUT TO BE A SUCCESSFUL AND UNEVENTFUL TKOF. HOWEVER; RWY 1 IS 500 FT SHORTER THAN OUR REQUIRED TKOF DISTANCE FOR THE DAY (2500 FT TOTAL RWY AVAILABLE). RWY 6 IS 5000 FT AVAILABLE. CONTRIBUTING FACTORS: MAINT DELAYS; UNFAMILIAR ATC PROCS WITH REGARD TO PICKING UP THE CLRNC (SHOULD HAVE BEEN PRE-TAXI). LACK OF RWY SIGNAGE (THERE IS NONE; OR EVEN PAINTED NUMBERS). POOR ARPT DIAGRAM INTERP (RWY 1 AND RWY 6 APCH ENDS INTERSECT AT CYSN). FAILURE TO CHK THAT HSI HDGS MATCH RWY HDG PRIOR TO ROLL; PARTICULARLY ON AN IFR DEP. OUR SAVING GRACE WAS A LACK OF MECHANICAL PROB; AND A LIGHT; HIGHLY OVERPWRED JET.