popping and spitting Solex carbs

[ghia70]

Hi All,

After a bit of advice.

Re-fitted the Solex P-40 carbs (Split Shaft) after refurb with new gaskets etc. Started car and got to fast idle but one of the carbs (RHS) cylinder 1 intake is popping and spitting. I've set the mix screws all the same approx 2.5 turns out. screwing in / out does not seem to make much difference in the intake. ignition has stayed the same (did not touch it) have replaced plugs and fitted a fuel pressure filter (set to 2.5 psi). any ideas on what i can try to get it running in a better way ?

Thanks

Danny

[Nine One One]

Check your ignition again, you or someone else may have compensated with the ignition timing for your previous carb set up?

Also check the intake manifolds with carb cleaner, see if that increases or drops off the revs, indicating you have an air leak. Are the surfaces of the manifolds with the head flat, gaskets correct?

[neilbardsley]

Do a bottom up tune? After checking the valve gaps. Change the plug and gap.

One of Jack's tests is pulling of the lead off the distributor cap. Which is how I found my bad spark plug.

http://www.356carburetorrescue.com/jackstaggs.html

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[Kneeslider]

When something runs badly, there is only one way for sure to catch that Gremlin, and that is the dull, boring and time consuming way of being really thorough.

Start by looking at the valve clearances, all of them. Next set up the timing. Look at the points, if you have them, check they are clean, and not pitted, and that the gap is in spec. Check the static timing, start up the engine, and then, look for full advance when it is revved.

Only then try to do anything with the carbs.

Checking for air leaks to the manifolds with a can of carb cleaner is a good test, but I have found that the throttle spindles on my split shaft Solexes leak quite a bit, they all leak the same, and that is after a company who are quite well known had a go at them. Looking at the way the throttle spindles go into the carb bodies, it is tricky to see how they can be made that much better, they have no discernable play. I think that they have been like that pretty much all the time. Maybe finding a way to fit some seals woud cure it.

My bet would be that the butterflies in are out of sync by a little, as you have split shaft carbs, you can adjust each carb individually with a synchrometer.

Have a look at all the jets, and make sure that they are all the same, cylinder to cylinder (check the sizes to make sure no one has drilled them out. Don't ask how I know...) and that the main jet holders in particular have the jets snug and that they don't leak.

Only when all these things are spot on should you think about adjusting the mixtrure screws.

Edit. Oops, looks like Neil got there before me!

[neilbardsley]

"My bet would be that the butterflies in are out of sync by a little, as you have split shaft carbs, you can adjust each carb individually with a synchrometer."

I think this might be the solution once you have checked all the basics. My understanding of solexes and the engine not responding to a mix screw is that the butterfly might be covering the hole for the idle circuit?

Check out these videos from Tom in the US. He is setting up webers but shows solexes in the 2nd video

https://youtu.be/juEd5RICWW4

https://youtu.be/2uDY1wcx6mo



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[ghia70]

Quick question for cylinder 1 carb butterfly adjustment where is the adjusting screw ? - is it in the centre of the card near the accelerator pump rod ?

Thanks again for all your replies

Danny

[Nine One One]

Quick question for cylinder 1 carb butterfly adjustment where is the adjusting screw ? - is it in the centre of the card near the accelerator pump rod ?

Thanks again for all your replies

Danny

Here you go, complete manual and instructions

http://www.lonestar912.org/912%20Tech%20Data/solex1.pdf

[Mike Smith]

Go to the Web
Bring up an Exploded View of the Parts - Solex 40 PII Carbs
Look for the 2 x Small Jets in the Top of the Car Body under the Top Cover - they are usually marked Part no. 33 and 34

These 2 x jets do a different job BUT the size and threads are the same - you may have reversed them in the carb. that is not working.

[wildtexas]

Hi All,

After a bit of advice.

Re-fitted the Solex P-40 carbs (Split Shaft) after refurb with new gaskets etc. Started car and got to fast idle but one of the carbs (RHS) cylinder 1 intake is popping and spitting. I've set the mix screws all the same approx 2.5 turns out. screwing in / out does not seem to make much difference in the intake. ignition has stayed the same (did not touch it) have replaced plugs and fitted a fuel pressure filter (set to 2.5 psi). any ideas on what i can try to get it running in a better way ?

Thanks

Danny

If adjusting the idle.mixture screw does nothing only on cylinder 1 which is popping, I would suspect a blocked idle circuit. Is it ok when you raise the revs and get it onto the main circuit? About 2800rpm.

Your could try removing the mixture screw and blowing through with compressed air or carb cleaner.

Matt

[neilbardsley]

Did you resolve this? I hope you tried Mike's idea before mine!

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[ghia70]

No Not yet, thought i would give it a break and start again . Im sure i had the jets in the right place as i remember checking but will check again and run through all of the suggested areas. I did take out for a quick spin - went Ok but still popping in the lower rev range / fast idle.

Danny

[KS]

Just had the same symptoms on my Weber 44IDFs - idle jet blocked.

[ghia70]

Hi All - Bit of an update.

removed carb today
checked small jets were in correct position - they were although one of the jets was not marked so put another 1.8 (position 27 Idling Jet on Solex diagram) jet in to match the other side. the two other Jets are 0.7 (position 34 on Solex diagram)
checked other jets and blew through to clear.
Re-fiited carb with new manifold gaskets and main body gasket
Changed condenser and points and reset
cleaned distributor cap contacts and rotors
Fuel delivery seems OK - fitted a pressure gauge (set just below 2.

Car started but same issues persist

Had to stop at this point as started to rain - all fun and games

Next steps
going to get an airflow meter and see what the measurements are

[KS]

Fuel pressure seems far too low to me - Elfrink says around 3psi for the Solexes.

From Porsche workshop manual:



0.2 ATU = 2.94psi
0.24 ATU = 3.5psi

[Mike Smith]

Fuel Pressure

I agree with Keith - we always set at 3.5 p.s.i