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Good evening all.
I have a GCV530 in a HF2417.
Suffering from engine speed stability (huntung) issues.
So far I’ve set the valve clearances, changed oil, oil filter, air filter and fuel filter, changed the plugs, checked the spark is working, put a brand new Honda oem carb on it, changed the regulator spring, changed the fuel pump and prayed to the Lawn Mower Gods.
Nothing works!
It is definitely running lean, spark plugs are white, and it’ll run perfect if i partially block the inlet manifold.
Please help before i throw a match at it.

Partially blocking the intake and running fine indicates a fuel delivery issue. So either the new Honda carb has a problem or you have an air leak between the carb at the intake manifold, or an air leak at the manifold to cylinder interface.

see above website to make sure you have correct carburetor. have you drained old gas & added fresh gasoline? did you replace carburetor gaskets with new?

Carb is EU model, correct numbers.
All gaskets and O rings replaced.
New fuel pump, filter, lines and fuel.

Update……..
Right cylinder is running at 280°C left is 480°C!
Both have 145psi compression. Valve clearances done.