Outdoor Power Equipment and Small Engines - Honda Mixture Screw Adjustment

The mixture screw adjustment has no effect on the mowers performance. The engine idles up and down but if you spray wd40 at the mixture screw it idles out ok. But when I engage the blades it runs somewaht smooth also. Any hints of the problem. I've taken the carb off and cleaned twice.

Largely could depend on what Honda engine you are reffering to? Also whether you have one or two mixture screws.
Some Honda's have the idle mixture on the base of the carb where it mounts to the intake. If you are spraying here and the screw has no affect, the carb could be loose (IE: Airfilter housing removed..?) or a leaking gasket. If there is a leak the WD-40 may temporarily seal the leak and allow normal idle. This could also cause the mixture screw to have no affect since it can not meter the air of the leak.

Really need to know what engine however for accurate info.

Its a honda 5 hp model hra-214 mower. It does have only one mixture screw as you metioned at the base of the carb. I did not replace the gasket but I did goup it up with form-a-gasket and I made sure to snug the carb relativily tight. I also checked with the dealer to make sure there was not a o-ring on the mixture screw. No o-ring.

Sounds like you need to soak the carburetor in a bath type cleaner (I like Napa #6402) and use OE parts. Check with your local Honda dealer for such parts.