I have a 2002 harley fatboy that I am trying to get my idle screw adjusted so I can get the right color of my spark plugs. ( by the idle screw I mean the one you have to drill the plug out) My service manual says the spark plugs should be 1 White 2 yellow 3 tan or rusty brown. My spark plugs are white and I get 42 to 44 mpg. My oil temp never gets over 200mto 225. I have a temp gauge that I measure the head by the spark plug and it never reads over what the service manual says (I can't remember what temp it says but it never goes over that temp) It never backfires through the carb and runs good through the entire speeds. I run 91 octane gas with ethanol in it (10 percent ethanol ) I have it set at 2 1/8 from lightly seated. All the posts I have read on the internet says the white spark plugs are running lean, but I cant get them any other color exept when I go above 2 1/8 turns out from lightly seated and then they are rich and they are really a sooty black. My compression is good. So is white the right color or what?

 

If you can’t make it richer adjusting the air screw a jet change may be in order but by the sound of it it’s running well so don’t screw with it.

 

If it works, don't fix it.

 

White is fine. Just means your engine is running cleanly and you're using a decent fuel.

Only if the ceramic section looks shiny/glazed do you have a lean problem.

 

I agree with all who have said you are good, no need to mess with it...

FYI....

There are three parts to an OEM CV40 carb that affect the air/fuel mixture; mixture screw, needle, pilot jet, and main jet

They each address a specifc range of operation, but of course they overlap in those responsibilities and need to work together..

Your mixture screw is working within an acceptable range, before suggesting the need to bump up the pilot jet another size.

You report it is running well, accelerating well, running cool, and with no backfires. Sounds like you have it dialed in..

FYI- If you just have Stage I mods (high flow air cleaner and high flow exhaust or slip-ons) you can often dial it in with just adjusting the mixture screw.