ok.... a few hundred of feet abv FL 140 ....but on the next flight just after reaching FL 100, press IAS on AFCS (so called pitch mode) and adjust the pitch at 4 degrees UP.....in 2 minutes you could see a vertical speed of 1000 FPM and an IAS of 190-210 kts(as you know it depends of ISA ,weight,etc) and after half an hour you can reach FL240 or 230....having a rate of climb of 4-500 FPM.....try it!