Running rich

[Mototech]

I've acquired a 1977 CB750 & it appears to be running seriously rich, plugsare very sooty. I have the carbs apart & from what I can gather,everything is as it should be. It has new electronic ignition fitted, new plugs & plug caps.   Are there any common issues I should look for?
Brian

[K2-K6]

Welcome to the forum.

Have you checked air filter for condition? Even if it's been left stored damp it can affect it.

Do you know what jets etc are fitted in size and if they are original Kiehin manufactured.

[Skoti]

Yep,

my F1 was once the same running very rich, after trying most things eventually new genuine needle jet kits cured it.

It's the only jet in the carbs that really wears out and most folk over look it.

https://www.cmsnl.com/honda-cb750f1-super-sport-1976-england_model14680/needle-setjet_16012392004/

[Mototech]

Welcome to the forum.

Have you checked air filter for condition? Even if it's been left stored damp it can affect it.

Do you know what jets etc are fitted in size and if they are original Kiehin manufactured.

All checked, filter new, jets all correct sizes.

[Mototech]

Yep,

my F1 was once the same running very rich, after trying most things eventually new genuine needle jet kits cured it.

It's the only jet in the carbs that really wears out and most folk over look it.

https://www.cmsnl.com/honda-cb750f1-super-sport-1976-england_model14680/needle-setjet_16012392004/

Definitely worth a closer look, there is no obvious wear, but might be worth changing anyway.