Which needle setting?

[TRFOXX]

Im putting a 40 pilot jet in tomorrow, instead of the stock 38 pilot in my 400ex and was wondering if I should drop or raise the needle any or leave it at the stock setting? I have a 152 main jet and 4 1" holes in my air box lid. With a FMF Powercore 4 slip on. Whats the advantages of this? What should be the correct set up for what I have? Need help! What will this do to the 400ex? I will still be able to use the same 152 main? I wont have to change it out will I. Any help would be great!

[SGA]

The pilot jet controls the idle to 1/4 rpm range. It should have no affect on the needle clip setting or the main jet. Many people change to a 40 pilot for easier starting when cold. If yours hesitates/bogs when you nail the gas after you put the pipe on, you will have to lower the needle clip one notch. If not, leave the clip alone. Do not rush with jetting changes, do one at a time and give it some time to run. You may have to go up on the main jet also a little. The spark plug color will tell you that after a wide open throttle run test. Remember that it takes a new sparkplug some time to get some color if you happen to put in a new one when you add the pipe. Read the carb basics in the extech link above, that should help explain alot. also look in the ''best of'' forum

[TRFOXX]

Thanks for explaining that, well understood! Ive already had the pipe on there so i guess I wont have to change the jetting. I will take another look at the plug though, I just put a new one in last week when I changed my oil. She has been running great with a 152 main jet, other than a little backfire at start up, but from what all you guys run I seem to be a little low on my main jet?