Zenith carburetta problems

[Ian K]

I have recently had my Ruby return and I have problems with the carb. It only runs with power when the choke is out and now won't tick over with the the choke off. I have cleaned the three jets in the float chamber but can't remove the progression jet. However I don't understand why a blocked progression jet would cause the lack of power without the choke. Any ideas?

["Slack Alice" Simon]

I have had similar symptoms from a failed ignition condenser.

If you have a spare, temporarily wire it from the ignition terminal on the distributor to a cylinder head nut.

If the problem goes away, replace the original condenser.

[Ian K]

I will change the condenser over the weekend but don't think that this is the problem. Ruby has been with a garage and has had the carb changed/ reconditioned. I'm not convinced that it has been rebuilt correctly. It did leak petrol and after checking that the float was ok changed the float valve which has stopped this. I will let you know what happens.

[Mike Costigan]

Air leak at the manifold?

[David Stepney]

Check to make sure the carb to manifold nuts are tight. I have had this problem with my RP. The symptoms were similar to that you describe and it wasn’t the most obvious fault.

[flywheel1935]

My ARQ is doing the same, and I've bought a new condenser too, as It seems load is causing a problem ???

[Ian K]

I changed the condenser and checked the manifold tightness and all were ok. Have found the problem when water started to appear from one of the head studs. The head gasket has clearly gone. I am starting to remove the head to see what's happened.

[Ian K]

I have fitted a new head gasket and yes the old gasket had blown. I still have a problem with the carb as it doesn't work properly unless i use the choke. Without it the engine will not rev and is clearly starved of fuel. Could the carb have been rebuilt wrongly? Is there anything I can adjust other than the screws that alter tick over speed and tick over mixture?

[Robert Foreman]

Ian,
       underneath the carburettor is a brass plug with a screwdriver slot in it. 
  Remove the plug and clean the jet inside with a piece of fuse wire. Do not attempt to remove the jet as it rarely will come undone.

[dickie65]

Have you checked the float levels, I understand the modern fuel is a different density which may affect the running.