Peirburg

[dandaz]

Hello

i had a engine fire and it burnt the red/brown plastic piece ,so I bought a second hand carb ,it is ok, but always felt it was`nt as smooth as my old one...Today I decided to swap the plastic piece over ,I ran it and it made such a difference ,very smooth then it stopped...

So I stripped it and cleaned it ,now it runs super super fast or without tickover...

I am having issues with the black round thing on the [front left on picture] ,it feels loose ,when I pull the shaft and races and have to pull it back it seams not connected to anything.......

decided to swap the new bottom with my original top made zero difference...

I am out of ideas...

[MidLifeCrisis]

The 'black round thing on the [front left on picture]' is the vacuum unit that controls the secondary throttle plate (which is the flap in the lower of the two venturi's tubes in your picture).
It can only operate when the primary throttle (the one controlled by the cable from your accelerator pedal) is about half open - so if you try to test it with the throttle closed then it won't work. Rotate the primary throttle fully open then the vacuum unit should rotate the secondary throttle flap in the secondary venturi.

Hope that makes sense.

[itchyfeet]

whs^^^

the first pic shows the primary throttle cam pressing on the secondary vac unit plastic cam, it can't open
the second pic shows the primary open and the secondary can then be pulled open by the rod connected to the vacuum unit.

If you can move the rod at idle then the plastic cam may have melted or broken

[dandaz]

it makes perfect sense

Trouble is both throttles can open fully without effecting this ie touching it the bottom bit [cream piece]....

does this bit have anything to do with the choke because I did break one and swap it over ,this is where the problems started.....?

[itchyfeet]

nothing to do with choke
That's a comepletely different mechanism

[dandaz]

itchyfeet

thanks for posting them most helpful ,should the rod that goes in the vacume ,be a bit loose?

[itchyfeet]

not sure what you mean,

the vacuum unit will move on the rod as shown in the picture, it's spring loaded so the spring is strong enough to pull the throttle open if it is allowed by the cam but allows the vacuum unit to move when the rod is held by the cam and so won't put excess load on the membrane.

[dandaz]

when I start the engine the flap that is meant to be closed is slightly open ,even when I take the carbe off and suck to make a vacume ,the butterfly still has not closed fully ,I cannot see and adjustment to make this close fully....When the carb is off I have 2mm gap between the beige piece and the throttle ...

I think this is my problem because tickover is too fast...



This picture looks like the flap is fully closed and the beige piece is touching the throttle..

[itchyfeet]

You say you had an engine fire so id assume damage rather than adjustment

[dandaz]

You say you had an engine fire so id assume damage rather than adjustment

cheers, I never thought of that...

[dandaz]

Changed the black thing over from the old carb and the van is running nicely, in fact very sweet....

BUT I start the bus and both battery and oil light goes out ,then straight away red battery light comes on....

all the wires are still on the alternator....