Hello,
I have an 12A engine converted in my car. It worked fine when i toke it out the mazda. But now the engine is built in another car, i have a problem. The thing is, when the secondaries open, the car coughs and dies. The primaries works fine. It idles nice and quitely at 500rpm and the car is very drive-able, as long i don't push the pedal to the metal. It makes no difference if i open the secondaries a little or all the way. It coughs and dies.

I have a lamdba sensor mounted and it reads for the primaries an good mixture, but the secondaries are very lean. So my first impression is blocked jets. I have cleaned the jets and passages several times and they are clean to me.

Strange is, If i rev it and look in the carb, i can see the secondaries open and i see fuel coming out! So that seems oke. But this is an stationary test and driving under load is different.

The secondaries are vacuum operated and i am quite sure it works properly. I also converted temporarely to mecanical secondaries, but that makes no difference for the dying secondaries. It is back to vacuum now.

The engine is mounted level so the carb is at a slight angle. It is tilted about 6 degrees. I experimented with some fuel level settings to compensate for this angle. But whatever i tried, it makes no difference. I have the fuel level now set at the standard correct height.

I have checked the fuelpomp and it gives much more than the 1400cc per minut it should do.
Ignition is set correct and if i disconnect the vacuum advance, it makes no difference for the dying secondaries. I even swapped the muffler for a original mazda muffler to see if that is the cause, but no...

The rats nest is removed and all the vacuum ports are blocked, except the second from the front (ignition advance). I have fitted a bigger airfilter but even with no filter the secondaries dies.

I am still suspecting the secondaries jets, but they are clean and a stationary rev test shows that there is fuel coming out.

I don't know it anymore. I have read lots off posts and i am sure that the answer is somewhere in this jungle of thousands posts. Can someone help me?

 

You may need a different carb. First check the emulsion tubes. They say 140 on top. Unscrew them and take a look. They should be clean. If not, clean and install.

 

Yeah, sure has all the symptoms of clogged jets....

 

Emulsion tubes and jets are clean.
What is the difference between reving it stationary or under load? Stationary shows the secondaries works but under load it tells me it doesn't.

 

When vacuum operated, reving the engine stationary will not open the secondaries.

 

Maybe yours don't but mine do open at stationary reving . I have taken out the spring from the vacuum diaphragm.
Do i have to fit bigger jets?

 

Well, my crystal ball is at the repair shop so if you fail to mention that little detail, how do you expect me or anybody to give you a sensible answer?

 

That's a possibility.