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rough idle issues


450rman

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Weber 32/36 carb is pretty new. Motor just rebuilt. I replaced plugs wires cap n rotor and coils. Idled good before motor was rebuilt. Now it idles rough and spark plugs are covered in black soot. All emissions vacuum lines have been removed beside carb to distributor. Any ideas?

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Soot is an indication the carb is running rich

 

 

Check the choke is fully off when warmed up. If not off...

Check that there is power to the choke heater when engine is running.

Is your alternator charging???? Choke won't shut off if no charge.

Check/clean/lubricate the linkage to free it up 

 

Check the float is not sticking or set to the wrong height on carb

 

Is there dirt caught in the needle valve at the carb inlet. Nedle valve not closing the carb will flood.

 

Was carb rebuilt? Primary and secondary jets may have been swapped by mistake.

 

You have stock fuel pump? Must be no more than 3.5 PSI or it will flood an old weber.

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Easy.

 

With engine fully cold, rotate choke until it just closes 100% when you open the throttle slightly. Then tighten it.

 

For easy starts and perfect cold idling, make sure it closes 100% when engine is cold. But also make sure its not any tighter than that or it may not open fully when warm.

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Your buddy is wrong. Automatic chokes have an automatic choke break which will automatically open the butterfly a little bit as soon as the engine starts. Check any repair manual for the facts.

 

Yes there is s Fast Idle adjustment screw. It should idle 1600-2400 rpm with choke adjusted correctly.

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Hmmm. Im baffled then. Dont know where else to look. What else could be causing it to run so rich at idle? It leaves a puddle under the tailpipe.

 

Already answered...

 

Soot is an indication the carb is running rich

 

 

Check the choke is fully off when warmed up. If not off...

Check that there is power to the choke heater when engine is running.

Is your alternator charging???? Choke won't shut off if no charge.

Check/clean/lubricate the linkage to free it up 

 

Check the float is not sticking or set to the wrong height on carb

 

Is there dirt caught in the needle valve at the carb inlet. Nedle valve not closing the carb will flood.

 

Was carb rebuilt? Primary and secondary jets may have been swapped by mistake.

 

You have stock fuel pump? Must be no more than 3.5 PSI or it will flood an old weber.

 

Drips from the tail pipe is just normal condensation. All vehicles will do it.

 

Idle fuel is unaffected by jet size. Idle has it's own fuel supply.

 

The '85 has no idle mixture adjustment as it is set and sealed at the factory. So do the following...

 

Be sure that the valve lash has been checked and set and that the ignition has been checked and set.

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Its not just drips. Its a big wet spot that leaves a big spot of carbon on the ground. One thing i didnt check is the needle valve at the inlet. I also know nothing about what jets should be where or what size they should be. If the timing was off by 1 tooth would it cause this?

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No i dont. I can get one tho. The only info i found on making sure the float was set at right height was really confusing. It said the float should be sitting level and should have 2mm of movement when you push down on it. Mine had way more than 2mm.

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