hello all , I did full tune up not a year ago with MR43T plugs, ran great then months later I notices rpm fluctuations at non wake speeds , and some carbon floating at startups , so I'm thinking carburetor issues ? . so pulled carb apart and it looked ok unless I missed something and it needs an adjustment , I also pulled the spark plugs to see the condition they were in , they were really black full of carbon sooty not oily and went as far as checking compression all 8 were between 140 and 150 psi I'm not sure what the culprit could be ? timing fuel what should I check next . thank you

Sounds like its running rich at lower rpms

If plugs are sooty, that's a lot of fuel. If you didn't change the idle mixture, I would check to see if you have a float sticking or needle leaking fuel. Used to have the same problem on my old 66 Grand Prix. Hit the carb with a hammer handle and the float would pop back up and it was fine until it wasn't.

thank you to all , I will look for sticking carb issue .

What carb ?
What did you use to clean ?
Did you replace and adjust needle and seat correctly ?
Which carb kit ?

Which engine ? What is the timing ?

What tune up parts ?

it's weber 9780 cleaned with gunk carb and choke unfortunately the carb kit is made in china , I'll just be using the gaskets from it cause the float seats don't even screw down lol , anyways a friend said to check choke and wiring, also installed a new fuel pump this summer and need to check the pressure from it . too much pressure like 8-9 pounds the fuel will get past the seats and cause this carbon issue I'm having also . thanks

Look down the throat of the carb with a strong flashlight immediately after shutdown. If you see fuel dribbling out, the needle/seat assy isn't shutting off the fuel for whatever reason.