The Sooty Show!

[Boomlander]

Hi All,
The car has been running rich with a lumpy tickover and sooty exhaust.
I turned the jet adjusting nut up a couple of flats and the engine ticked over slightly better but it is still blowing the black stuff onto the ground.
Is it just a matter of turning the nut up further or do I need to think about a new carb?

[Tom and Maria]

Have you taken it for a good run?

It might just be condensation from the exhaust picking up soot from previous rich running. It will need a good long run to get rid of it (especially in this damp weather).

What colour are the plugs after a good blast?

Tom

[JOWETTJAVELIN]

If worse comes it a rebuild kit: no need for a whole new carb. Black on floor is normal soot.

[bmcecosse]

It doesn't need a new carb...... Take it for a good run - then pull out the plugs and inspect the colour. Should be light beige.

[mike.perry]

Wind the mixture nut up a flat at a time until the engine starts to slow down. The nut should be about 2 turns down from the top

[Boomlander]

After a run the plugs were black but dry and sooty, the jet adjusting nut was almost at the bottom of its travel to begin with so I will warm the engine up today and tweak the nut up to where it should be and see if it cures the problem.
Many thanks folks.

[David53]

As Mike says, a couple of turns from the top. If its right down the bottom then you are definitely far too rich

[JOWETTJAVELIN]

Rev it in between small adjustments to see the effect, just idling is no good as it takes a while for the petrol to flow through.

[Boomlander]

Sound advice - thanks again guys.

[Boomlander]

I noticed that the carb fitted to my 948cc engine is the HS2 type with the nylon fuel pipe from the float chamber to the carb.
The manuals list the carb for 948 engine as the H2.
Is the later carb OK for the 948 engine or should I fit the H2?

[bmcecosse]

It's better = keep it.

[Boomlander]

Much obliged Roy.