An HS125 Captain became distracted by unexpected turbulence while leveling IMC at 1;500 FT on the TEB RUNWAY 24 SID and climbed to about 1;800 FT before descending to 1;500 FT. The Reporter is very experienced on TEB departures.

Narrative

Departing Teterboro on the TEB6 Departure from Runway 24. SID calls for initial heading of 240 degrees in a climb to 1;500 FT then a right turn to 280 degrees. Maintain 1;500 FT till 4.3 (4.5?) miles; then climb to 2;000 FT. I have flown this departure numerous times; having operated irregularly into and out of Teterboro for the last 10 years with five different aviation services companies. I expected to go into the weather at the initial level-off at 1;500 FT but did not expect the turbulence; not severe by any means; just more than I had anticipated; and I will also admit to a distraction in flying the airplane as a result. As I made the turn to 280 degrees; I did not level-off per the SID. I am well aware of the emphasis; and the reason for such emphasis; on maintaining good altitude control. New York told me to hold 1;500 FT. I don't believe that I went more than about 300 FT high - not an excuse; just a fact. This incident is sitting in the pit of my stomach; as I know it should. An experienced aviator; I am most embarrassed by my actions. It should NOT have happened; but it did. Apologies would not make up for an incident with EWR arrivals; I know. I can only assure you that I will take the extra moment required to re-review the SID on each and every departure.