Still running rich after mixture screw adjustment

[B0ndy]

Yesterday I took a bike out which I've been doing alot of work on recently and noticed that it's still running rich despite adjusting the mixture screw on all four carbs.

It seems like no matter how much I adjust the mixture screw, the bike still shows all symptoms of running rich whenever I take it out; runs badly when warm, heavily fouled spark plugs.

Any suggestions please?

Bike is a CB400 NC31

[RhynoCZ]

Tell us, how exactly do you fiddle with the mixture screw? Have you checked the air filter? If it's too restrictive, you get rich mixture. The same applies to the choke. If it's stuck, rich mixture is what you get.

All that above if the jets are stock, if not, there's the answer to your problem.
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'87 Honda XBR 500, '96 Kawasaki ZX7R P1, '90 Honda CB-1, '88 Kawasaki GPz550, MZ 150 ETZ
'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor

[unitynotsocri...]

Or a mangalled float height?
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