Weber not idle right

[yelcab1]

I am rebuilding and setting up a set of webers for my neighbor 914-6. They were disassembled, cleaned, 45 idle jets were thrown out in favor of 55 idle jets. No blockage was found. The accelerator diaphragms were changed, all four needle valves were changed, O rings and gaskets were changed. Points, condensers,rotor and caps are new. They are now balanced but still occasionally spit a bit.

1. The carbs will not idle unless the two idle stop screws are turned in 2-3 turns.
2. They will be slow to come back to 1000 rpm when they are revved up to >3000 RPM.

No binding of cable is found.
Compression is good. Timing is set via static timing mode. Valves are well adjusted.

Any thoughts? I don't play with carbs enough to get really good at it.

[JohnJL]

What size and cam is the motor?

[JohnJL]

Also, is the ignition system 100%? a weak spark or fouled plug will have you chasing your tail with carbs, esp during initial tuning. What plugs?

[docrodg]

Throttle plates are centered in the throat? If off a little it could be loosing signal to the idle port and thus only idling when you turn the idle up to the point the progression circuit is kicking in.

[yelcab1]

Stock 2L motor and cams.

Throttle plates are well centered. They were all checked when the carbs were done. All butterflies close off nicely against the bodies.

Ignition seems OK. No foul plugs, and plugs are brand new as well from PP. Ignition was set when the engine was out using the static method right at Z1. Now that the thing is in the car, it is impossible to check ignition on the 914-6 with the engine facing the firewall. Any tricks? I could experiment a bit with dynamic timing by turning the dizzy a tiny bit.

[DaveA]

This sounds like it could be weak distributor advance springs, or a sticky distributor advance. If the advance mechanism does not pull back to zero at idle, it will cause the engine to run fast. Pull the distributor cap off, and work the advance by turning the rotor and releasing. Pull the rotor off and add a few drops of oil to the felt in the middle of the rotor shaft. Finally, check the advance with a timing light to see what is going on.

R/Dave

[Jack Stands]

I'd look at the timing first. 914-6 engines can have their timing checked by using the timing marks that are embossed on the flywheel. Look just behind the engine breather and you should see the location where you can see the flywheel and use a timing light to check the advance.

[haasad]

Idle circuit on the carbs? common prob usual fix is to drill the circuit bungs manually clear them and re bung. My r car ( and several others) displayed exactly the symptoms you describe even after multiple ultrasonic cleans etc. Frustrating thing is often its not obvious that a blockage has been cleared but the motor runs fine after

[yelcab1]

Originally Posted by haasad

Idle circuit on the carbs? common prob usual fix is to drill the circuit bungs manually clear them and re bung. My r car ( and several others) displayed exactly the symptoms you describe even after multiple ultrasonic cleans etc. Frustrating thing is often its not obvious that a blockage has been cleared but the motor runs fine after

I did this and it got the Cyl2 to respond to the idle screw now. So, that is positive. The remaining issue is 1) not idling unless the stop screws (1 each carb) are in 2-3 turns, and 2) slow to return to idle.

I will check timing through the little port next.

[docrodg]

Just re-reading your post. Problem 2 sounds like it could be an air leak, which could cause problem 1. If air is getting in below the throttle plates it would take away signal from the venturies.

[roblav]

Agree with sticking distributor advance...