I was running rich. I knew this because the plug was black. So I did the carb adjustnment exactly like the Honda Service manual said. Start 2 1/2 out with idle at 1400. Turn pilot screw in until the engine stops, then back out 1 turn. This put me at 2 turns out. I was 3 1/2 turns out. Everything seems fine, although it doesn't idle quite as smooth as it used to Anyway, how do I know if I'm where I'm supposed to be, exactly? How can I be sure I'm not too lean? I don't want to overheat and hurt it.

 

If the plug is showing white "hot spots" that is a good indication you are running lean. So look for any whitening.

A perfect running mixture the plug will be the same as it was when it went in, or slightly yellow..... anything too far from the original color is not good.

 

I would certainly check the plug, but keep in mind that modern fuel additives will often confound your efforts (vs the old days with leaded gas).

Running hot and deceleration backfire, are good signs of a lean condition. But, if all you did was some small changes to the idle circuit (1.5 turns to the fuel screw), I doubt you will be going from rich to full on lean just doing that small change.

 

Is it a 2-stroke or 4-stroke.

If a 2-stroke you have to look at the top of the piston to get a true reading. If it is 4-stroke the plug check will be fine. Should be a cardboard brown to some-what darker.

 

Also, when did you check the plug.

After a good WOT run or where you just putt'en around the yard!!!!

 

Ok, here's some more info:

It's a 4 stroke, 1987 250X

I checked it after a good WOT run, then hit the kill switch with the throttle still open and in 2nd gear, and let it die

I didn't have deceleration backfire at 3 1/2 out but do have a little now at 2 out.

After the WOT run, the plug was a little brown but did have some whitish spots. Hard to tell though since it is the same plug I had in when I was rich.

Should I put a new plug in and do the same WOT run?

 

Not nessasary to leave throttle open when hitting kill switch. Just let it coast to stop.

Sounds like you need to go back to 2 1/2 or 3. Sounds from your post that the plug is fine.

Just ride it.