solex 34 pict 3 mixture settings

[vwcamper]

My bus was running abit rich(black exhaust smoke and sooty plugs) so i tried setting the carb as it says in the haynes manual but when i screwed the volume control screw all the way in and then 2 1/2 turns out, it would'nt run properly and i found that it runs best when its 5 1/2 turns open from closed! why would this be?

 

[BJ1]

Possibly because your idle jet is partially blocked. Screwing out the vol screw compensates for this at idle but of course gives an over-rich mixture at higher revs - hence the sooty plugs (and low mpg). So take out the idle jet and clean it up.

Is this a proper Solex or some Bocar junk? If it's Bocar then the idle jet is sent out partially blocked from new because the 'manufacturers' (I use the term loosely) make the idle jet chamber too short. You can compensate for that either by inserting a thin washer under the jet, in which case it will perhaps tick over, or by taking off the carb and hitting it enthusiasticly with a lump hammer then using it as a fishing weight.

 

[vwcamper]

Yes its a proper(pain in the arse) solex, when you say idle jet do you mean the air by pass screw?

 

[Bookwus]

Hiya vwc,

While I too would be concerned about the maker of your 34PICT3 (you're really much better off with a Solex), turning the screw in and bottoming out, then turning it out 2.5 turns is only the starting point for a 34PICT3 carb adjust. The 2.5 turns out should put the carb in range in order to start the car. 2.5 turns out is NOT meant to be the final adjustment setting.

Check out Rob & Dave's website for a complete step-by-step in adjusting that 34PICT3.

 

[robins]

this is where Mike meens http://www.vw-resource.com/34pict3.html" onclick="window.open(this.href);return false;

rich

 

[vwcamper]

On the step by step guide it says, 13. Then turn the Volume Control screw back IN (clockwise) very slowly until the engine speed drops by about 20-30 rpm (slightly leaner). I thought that screwing the srew in (clockwise) richens the mixture?

 

[cyberdyne systems]

On the step by step guide it says, 13. Then turn the Volume Control screw back IN (clockwise) very slowly until the engine speed drops by about 20-30 rpm (slightly leaner). I thought that screwing the srew in (clockwise) richens the mixture?

When you turn the volume screw in (the smaller of the two - mixture) it allows less fuel in, there by leaning the mixture. As the others said check your idle jet (pilot) its on the opposite side of the carb to the adjustment screws.

5 1/2 turns out is too much and indicates a problem, most likely that air is being drawn in where it shouldn't (gaskets, rubber boots, throttle shaft etc), and your compensating for this by increasing the fuel with the mixture screw. If you have a servo make sure the pipe is good too, I had a crack in my rubber hose and it allowed the brakes to work fine but made setting the idle and mixture difficult unless i turned the screw out too far, now that is sealed again I could return the mixture down to 2.5 turns and fine tune from there, and it runs so much better.