Hi,

I'm going to break this down just so I'm clear, if any of the points aren't correct shoot back.

• You replaced the carburettor with a known good one
• You know the engine runs when it has fuel by priming through carb
• Fuel is not getting to carb by usual priming routes (choking)
• Fuel line is dry
• Engine ran previously fine

Couple of things left to consider:

• Your tank and specifically your clunk line. Do you run a felt filter, inline filter or no filter? If felt or inline check these aren't gummed up from old fuel residue. Check your pickup line for tears. Maybe try putting a fuel bottle for gravity feed above the engine and try starting it.
• Does your engine have an internal or external pump pulse? If external replace the line, check for blockages. If internal remove the carb and ensure your gasket or other debris isn't blocking the pump pressure hole on the crankcase and carb.

I'm no expert but over the past few weeks I've been struggling with an old (but new) CRRC 45 engine that would run erratically and I just could not get a tune. Eventually after a carb rebuild, new gasket on the carb to crankcase and new lines throughout just today I got a tune that I'm comfortable with. That engine just will not prime or pull fuel into the lines without dropping some fuel into the carb a couple of times. I don't have a power starter. Another annotation, I have a hedge trimmer that had intermittent starting issues. Eventually it wouldn't run at all. I was going to throw it out but decided to check the fuel lines. They were snapped off at the tank. Replaced them and engine runs fine.