A PA31 ATX PLT RUNS OFF THE END OF THE RWY AFTER ATTEMPTING AN AIRBORNE ABORT.

Narrative

I TAXIED OUT FOR TKOF COMPLETING THE RUN-UP WHILE TAXIING. DURING THE RUN-UP; I OBSERVED A 300 RPM DROP ON THE R ENG WITH THE L MAGNETO OFF. AS I HELD SHORT IN POS FOR TKOF; I INCREASED THE RPM TO 1800 RPM AND LEANED THE MIXTURE IN AN ATTEMPT TO BURN OFF THE FOULED PLUG. THE TWR THEN CLRED ME FOR TKOF; AND AS I ROLLED INTO POS; I CHKED THE MAGNETO ONE LAST TIME ON THE R ENG. THE R MAGNETO DROPPED VERY CLOSE IF NOT A LITTLE OVER THE 175 RPM MAX. I ELECTED TO PERFORM THE TKOF; HOWEVER; I STILL HAD AN INKLING OF DOUBT ABOUT THE MAGNETO. I ROTATED AT ABOUT 85-87 KIAS. AN INSTANT AFTER ROTATION; I CLBED 6-12 INCHES INTO THE AIR; THE STALL HORN ACTIVATED; AND THE ACFT SUNK BRISKLY BACK TO THE RWY. IN MY JUDGEMENT; THE AIRPLANE WOULD NOT FLY; SO I PROMPTLY ELECTED TO ABORT THE TKOF. SOON AFTER THE DECISION TO ABORT; I REALIZED I WOULD NOT BE ABLE TO STOP ON THE REMAINING RWY; SO PULLED THE MIXTURES TO INSTANT CUT-OFF; MASTER OFF; AND MAGNETOS OFF. THE AIRPLANE STOPPED APPROX 100 YARDS OFF THE END OFF THE RWY. NO ONE WAS INJURED AND THE ACFT WAS UNDAMAGED. I BELIEVE THAT THE CAUSAL FACTORS WERE: 1) HURRIED PACE THAT WAS NOT CONDUCIVE TO A THOROUGH; UNHURRIED RUN-UP. 2) NOT TAKING THE TIME TO BE SURE THE MAGNETO WAS OPERATING AT 100%. 3) A FAULTY STALL WARNING INDICATOR THAT WAS KNOWN BY OTHER PLTS TO HAVE GONE OFF PREMATURELY. OFTEN THESE OTHER PLTS WOULD PULL THE STALL WARNING CIRCUIT BREAKER AND LEAVE IT THAT WAY. I NEVER NOTICED THE PROB ON MY LIMITED (12 HRS) AMOUNT OF EXPERIENCE FLYING THE AIRPLANE. 4) THE AIRPLANE WAS 126 LBS OVER GROSS WT. 5) POSSIBLE MODERATE WINDSHEAR.