CV36 pilot screw outlet insert?

With reference to the Keihin CV36 carbs on an '83 440LTD. I'm having difficulties with the left side cylinder running very lean. Carbs have been thoroughly cleaned. New carb boots and all the airbox components are new. New carb kits etc. Carbs have been visually synced on the bench. I really don't think its sucking air from any leaks.

Bike runs ok. Starts and runs ok but always very lean on the left side. Was going to vacuum sync the carbs today but decided to pull the pilot screws again just to check that everything was in place there. The screws, springs, o rings and washers are all new. Running the pilot screws 3 turns out. The left side pilot screw has always felt course when I adjusted it.

My question is this. Looking down into the pilot screw holes the two sides look different. The right side carb which seems to run fine looks like it has an insert at the bottom to accept the tip of the pilot screw. The left side does not have this feature. Is there an insert in the pilot outlet that accepts the tip of the screw? (See #4 in attached pic) Can they be lost when cleaning? Can they be replaced? Seems to me if that insert was gone more air would flow through that pilot circuit and it'd run lean. 

Sorry no pics (I tried but can't get a good pic of the difference). Appreciate anyone's input. TY.



 

If never seen an insert for a pilot screw. If the hole is bigger than on the other carb, somebody may have damaged it. If so, you may never get it to work correctly. 

That is a fuel screw. Fuel is fed to it through the passageway represented by the dashed lines in the diagram. If the hole is buggerd up, it will flow too much fuel.