Grey plug.

[Iliketogofast]

Spark plug is a light grey color on the ground strip, and a has a small area of tan on the core part (the white inside part).

I figured it was lean because of the grey, but somebody told me when I showed them that it was ok.

Is it lean or good?

[Iliketogofast]

Okay, after another couple of runs the ground is still grey and now the tan area on the white part that surrounds the electrode is gone. That part is completely white now.

[GPracer2500]

Your description sounds lean.

[Iliketogofast]

Great.

[bwamos]

Aye, lean.

You check the ceramic insulator part for color. I'd go up 2 sizes on your main.

[ohsobad_chevy]

Ive always heard people say that running it a little (not too much) leaner, that it will give you a little more power, Is this a bunch of bull****e or what? I also heard that if you run a 4 stroke a little rich (like the 400ex's are from the factory) that it will make your engine temp stay a little cooler. Just some rumors that Ive always wondered if they were true or just some yahoo yappin his mouth.

[400exstud]

I have my 400 jetted pretty lean but I haven't had any trouble with it.

Your two stroke is a whole different beast though.

[Iliketogofast]

It was lean but the fuel air screw seemed to fix it. After turning it out 1 full time, it seemed to richen it up considerably.

I had the screw at stock settings because I had it out trying to figure out how it worked.

[bwamos]

Originally posted by ohsobad_chevy
Is this a bunch of bull****e or what?

In short, yes.

But, more doesn't mean more power either. You have to find the right balance.

14.7:1 is pretty much where (theoretically), where you are going to burn all the fuel, and all of the O2.

Now, going any leaner than that does nothing but make you bog down.. no fuel left to burn.

Running at 14.7:1 gets you great gas mileage and great emmissions, but not the best HP. It runs hotter than say a 13:1 ratio. When air get's hot entering the head/intake ports.. it expands. Which means, less O2 per CC. Less O2 burns less fuel, so Less Fuel and less O2 = less power.

Running 13:1 - 13.5:1 will help you run cooler. Since all of the fuel isn't completely burnt. Cooler air entering the cylinder (through the head) means denser air wich means more O2. More O2 to burn the fuel, so you get more boom.

However more fuel, isn't always better either. There's that fine line where you aren't getting the returns on cooler air to burn that extra fuel, so you start getting sluggish, and leave more unburnt carbon to foul out your plugs.

This is by far not a complete explanation, but just my random logic on the subject.

[GPracer2500]

Originally posted by ohsobad_chevy
Ive always heard people say that running it a little (not too much) leaner, that it will give you a little more power, Is this a bunch of bull****e or what?

This is true. But don't let it guide your jetting. The difference is small and if anything, your engine will be happier being a little rich.


I also heard that if you run a 4 stroke a little rich (like the 400ex's are from the factory) that it will make your engine temp stay a little cooler...

Yes, running a little rich does keep your engine temps cooler. That's why your engine will be happier being a tad on the rich side. An old rule of thumb is to keep going up on your main until it's too rich and then backing off one size.

Stock jetting on a 400EX is not rich though. For most locations it ends up being a little lean. The jetting is set up from the factory so that the engine will run satisfactorily at sea level AND at higher elevations (like say, 6000+ feet). The only way to do that is to be lean at lower elevations (where most people live). If a 400EX is jetted correctly for sea level than it will not even run at 9000 feet. The other reason for lean stock settings is emmissions.

[DieselBoy]

lean, in any engine, hands down, is NOT good.