I have an '89 Pilot that runs great here near Bakersfield CA., about 500ft. above sea-level. I'm planning to go to Pismo Beach Dunes in a few days, and remember someone saying I might need to rejet it for the beach. Will I have to rejet for the conditions of the beach,and if so where should I begin Main-Jet, Needle-Jet etc.???? Any info will help!!!!

It depends a lot on your current jetting most machines are jetted on the fat side, I doubt if you go form 500' to 0' that you will see a big requirement for a jet change unless your already on the lean size, the best thing to do is check your jetting when you get there to verify what you have.

http://www.pilotodyssey.com/carbtuning.htm

I doubt you will even notice a difference in the performance even with a 1000' change.

What you would want to worry about is if you had leaned out your carb to run better in higher elevation (say 2500' +) and then went down to sea level, this could lean the mixture enough for do damage. Going the other way (from low elevation to high) will only hurt performance or foul a plug.

Most of my stuff is jetted 0' to 500' and i have no troubles until i get in near the 3000' mark. At which point it gets so rich i will notice a hesitation/ blubbering at or near WFO with some noticable decrease in performance.