Now I am confused.

I put a 48 pilot in my 08 YZ450F. When it was colder out with a 45 in it I had to run the fuel screw at 2 1/2 turns out.

Now that I have the 48 in it I tested it on a little bit warmer day and it ran the best at 1/2 turn out.

My question is: As it gets warmer am I suppose to be leaning it out? Meaning turning the fuel screw in? If so then I need to go back to the 45 because I have no where to adjust to.

Everything is stock except for merge AP spring and full FMF 4.1 exhaust.

You are correct, when the temp is colder you need more fuel, the same reason you have to use the choke on a cold motor so to speak. I would put the 45 back in for warm weather if the fuel screw is in that far.

Yep cooler winter = richer

warmer summer = leaner

I usually change mainjets, and fine tune with pj's

1/2 turn on fuel screw is not enough - over 3turns is too much

range for me is 1.5 - 2.5 turns out

I put a 48 pilot in my 08 YZ450F. When it was colder out with a 45 in it I had to run the fuel screw at 2 1/2 turns out.

Now that I have the 48 in it I tested it on a little bit warmer day and it ran the best at 1/2 turn out.

If you are running at 1/2 turn out, your pilot jet is too large.

http://www.thumpertalk.com/forum/showthread.php?t=327405

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