F*%King Carb..........

[Nick k]

Need some info on how exactly the carb works at a certain point??

Right this is what i know.

On boost its fine,
It idles fine,
Swan neck jet working correctly so intial fuel input when pedal pressed.
No air leaks
No fuel leaks
Good fuel pressure.
Mixture screw good.

Problem is it got a massive flat spot between foot press and when it start to come on boost and then the enrichment kicks in and it goes ok.

All jets are correct

If i strip the carb, clean it and put it back together it will run mint for a while then it gives up again.

It had this flat point before where you would back off then press again and it would hesitate for a second then go, but the hesitation was after the intial swan neck input.

I reckon there is some crap in the main body thats blocking it. and me cleaning it is moving it about until it blocks up again??

Any idea's???????

Does all the fuel enter the venturi thought that hole thing in the middle with the brass rod under it or is the enrichment part feed in seperatly elsewhere???

Cheers.....

[Brigsy]

Ill place a bet its going very lean when the flat spot happens. Have you tried adjusting the arm on the acc pump jet? sometimes a bit of adjusting sorts it out.

Some carbs are a pain to sort out when they do this, a bigger main jet sometimes works but is a bit of a bodge!

[Nick k]

When it happens its more splutter splutter than a intial flat spot, like there is a blockage somewhere. And i blast it with the air line and its fine again for a few mins??

Going to file the carb under "B" for bin and just get another one on it. Can't be arsed to keep taking it apart!!!

[Alastair]

Nick, if you have a spare i'd use that, as Brigsy says, some carbs are just a pain. You will probably find a load of dirt under the emulsion tube (if you can get it out) that is moving around behind the main jet.

Oh and as per Brigsy have a go at tweaking the acc pump jet arm once re-set using 5mm drill bit check...

[Nick k]

Emulsion Tube?? is that the tube that going to the venturi?? You have to remove the metal stud thing holding it in??

[James5]

Emulsion Tube?? is that the tube that going to the venturi?? You have to remove the metal stud thing holding it in??

It's the one the air corrector jet screws into

[Nick k]

the brass tube that sits next to the swan neck pipe on a slight angle???

[James5]

the brass tube that sits next to the swan neck pipe on a slight angle???

Yeah to get it out screw one of the carb top bolts into the air corrector hole and pull fecking hard sometimes they come out fairly easily others are buggers

[Nick k]

Result It came straight out Cheers boys, never knew about that Will feck about with it tomorrow ......

[Sparkie]

Problem is it got a massive flat spot between foot press and when it start to come on boost and then the enrichment kicks in and it goes ok.

Does all the fuel enter the venturi thought that hole thing in the middle with the brass rod under it or is the enrichment part feed in seperatly elsewhere???

Cheers.....

all enrichments lead to the same chamber under the air corrector.

this flat spot.... does it happen when you're in 1st and 2nd, or when you are further up the gears? - ie does it happen when you rapidly plant your foot, or is it more to do with the period when the engine is just coming out of vacuum and onto boost? what turbo are you running? - reason i ask is the bigger the turbo, the longer the engine spends in the vac/boost limbo area. which is governed by the 1st stage enrichment. - which is why scoff and co always recommend to make it smaller! to stop it overfuelling in that cross over area.