Dont Understand why running lean

[Gommer450r]

i have an 2006 yfz450 with only mod is spark arrestor out
i had to put in a 170 main and a 48 pilot and needle all the way up to run right and still a bit lean tried sprying everything down with carb cleaner on my boots to see if there was a crack or a leak and idle never changed so no leaks anywhere i know a 48 and a 170 main way to big for stock application
also i em at sea level

[ohsobad_chevy]

Are you absolutely sure you are lean? You really can't go by spark plug readings. Have you had it on a dyno?

[Gommer450r]

no dyno around here
and noone knows anything bout 450's around this area either
buit with this set up my plug is darker than it was but still wish i could make my plug black then go from there to lean it up some i cant even go to that point

[Flynbryan19]

Plug color only tells you if your heat range for your plug is right.

The easiest way to jet is by feel(ie: change and test ride).

[Gommer450r]

what if i went to a cooler plug? cr8 somthing in it now?

[Flynbryan19]

Theres really no reason for a need to go to a colder plug.

What makes you feel that you are lean? Again, if you are basing it simply off of your insulator color on your plug tip your basing it off the wrong thing. What is the QUAD doing? Is it surging? Missing? Lazy? Explain what the quad is doing and where in the throttle/rpm range.

[Ride1Rob]

I've been jetting my bike based on what the plug tells me for years and it doesn't miss a beat. During this process I also use the butt dyno as well. The plug is a starting point for me as to whether I need to move up or down in jet size.

How is the bike running? Is it sputtering a bit anywhere in the powerband? Also, what kind of fuel are you running?