The carb is the symptom, not the disease.

You’re not choosing between carb cleaner and new fuel lines — you’re doing both, but you start with the fuel system.

Old gas leaves varnish everywhere. That varnish clogs the carb jets, but it also leaves deposits in the fuel lines and filter. If you only spray cleaner into the carb, the old gunk still sitting in the lines and tank flows right into your freshly cleaned carb and clogs it again. If you only replace the filter and lines, the carb is still gummed up and the engine won’t run anyway.

So do it in order: drain the old gas, replace the fuel filter, check the lines for cracks or soft spots (replace those too if they’re questionable), then pull the carb and soak it with proper carb cleaner — not just a quick spray down the throat. Fresh gas with stabilizer when it goes back together.

Yes, it’s more work. But it’s less work than doing the job twice.