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Thu Dec 26, 2002 1:31 pm

I have a '69 bus with a single-port 1600. Today I intalled a new solex 31-pict3 carb. I can get it to idle well and it works alright at higher RPM's but it hesitates between idle and running. For example, when I shift from 1st to 2nd gear the engine will want to stall. I've adjusted both the air-by-pass screw and the small mixture screw several times but all I seem to change is the idle speed or the volume of air entering the carb (the carb makes more noise as more air is taken in). Any help would be much appreciated.

Thu Dec 26, 2002 5:24 pm

Try checking the accelerator pump linkage, look down the carb with a small mirror if you cannot get your head above the opening enough. (with the engine NOT running of course) and pull on the throttle arm and see when it starts to squirt and how muh volume, and where at the butterfly the stream of fuel is shooting...
Also have you checked your points and timing as of late, which distrib do you have?

Thu Dec 26, 2002 7:04 pm

The '69 calls for a 30-pict2. That air bypass carb is designed to work with a vacuum retard. The '69 does not have a vacuum retard equipped distributor.
You will never get a good transition from idle to running in your present configuration.
Colin

Sat Dec 28, 2002 12:33 am

So it isn'texactly the same carb as the one I removed. The new carb obviously has an air bypass which I would guess was added for emissions on later VW's. Is there any way I can make it work with this engine since $100+ carbs are not returnable? Can the vacuum retard be bypassed or hooked up in some way? Also, where on the carb is the vacuum hose supposed to be attached?. As a side note, the distributor on the engine does not have a vacuum advance and it looks original.
It is possible that the timing could be off, I have not checked it. Could be the timing be the sole cause to the hesitation or is the carb definitly going to be a problem even if the timing is on spec.
Any help is much appreciated, Thanks, John

Sat Dec 28, 2002 8:43 am

If your distrib does not have a vacume advance "can" on it then it is likely an 009, which if not timed correctly will cause hesitation troubles.

Many try and blame the hesitaion strictly on the distributor but the carb itself and the way it is set up has equal blame in most cases.

Some carbs just CANNOT be made to completely eliminate the flat spot with the 009 however they may work well with a stock distrib.

But first NO MATTER WHICH DISTRIBUTOR you have, checking and replacing the points and setting the timing correct for that distibutor...
(not just "year model"... and depending on which stock pulley and which timing marks are there to confuse you!)
... is the first thing you should do before even trying to get more than a gross running/idle adjustment to any carb setup.
Then after you are sure the timing is set correctly( boy, there are alot of old threads on here about that, so I will not include that info here!) and you adjust out the carb and make sure the accel pump in squirting the right amount and the stream of fuel is pointed at the opening edge of the butterfly by positioning the squirter tube, check the timing again!

and make sure the distributor advances properly, the mechanism in the 009 and some others can get frozen in one place and or sticky and not move through the curve smoothly, you would notice this by watching the pulley/ marks while flashing with the strobe light and reving the engine from idle

After eliminating timing and for the most part the carb adjustment set-up, and the distib/ timing issues... hesitation can also be caused by; Loose heads and poorly adjusted/tight valves, improper type/ brand of spark plugs and or gap set wrong( beware the bosch platinums! use regular Bosch supers), vacume leaks, poor quality fuel,
weak condenser and coil/ spark plug wires (all these can " breakdown" under load...

In otherwords don't give up too easy and blame any one component without properly starting from a good base and eliminate ONE THING at a time.... good luck

Sat Dec 28, 2002 3:00 pm

johnkennedy7@hotmail.com said... (12/27/2002 at 11:33PM PST)
>So it isn'texactly the same carb as the one >I removed. The new carb obviously has an >air bypass which I would guess was added >for emissions on later VW's. Is there any >way I can make it work with this engine >since $100+ carbs are not returnable?

John,
Which side of the carburetor is your fuel cut-off solenoid? A factory-supplied 30-pict3 on the 1970 Bus has it on the right side nearest the generator. A factory-supplied 34-pict3 on the 1971 Bus has it on the left side nearest the coil. Your *31* is a mystery.
Colin

Sat Dec 28, 2002 11:12 pm

Thanks for the help/timing information keifernet. Hopefully with a valve adjust and timing check I can get it to work.

As for Colin's question the fuel cut-off solenoid is on the left (coil side) of the carb. It is located on the lower portion of the carb somewhat below the idle/air adjustment screws. From this I would guess that the carb may be similar to a 34-pict3.

Thanks for the help, John.

Sun Dec 29, 2002 11:12 am

"Your *31* is a mystery."
Colin

I gather that the carb is a new replacement
Brosol 30/31 carb( that is what is cast on the side of the float bowl?), which will work on single ports to replace the 28- 30 series solex or on dual ports with the adapter plate to replace the 34-pict 3 carb. yes it is very similar to the 34 with the fuel shutoff solenoid on the left side of the carb... make sure the solenoid "clicks" when it is energized (hooked to + side of coil) and that it is tight in the carb. if it is loose even slightly it can cause ilding running trouble...
Check the other stuff, especially the points (use new Bosch points not generic) gap them correct and check the timing, look on the distib and see if the #'s say it is an 009 and time it correctly. then post if you have success or any other troubles still...

Wed Jan 01, 2003 10:55 pm

>amskeptic@mindspring.com said... (12/26/2002 at 6:04PM PST)

>The '69 calls for a 30-pict2. That air bypass carb is designed to work with a vacuum retard.

Say What??? That's total nonsense - the 31 series carbs NEVER had a retarded ignition as far as I know - that vacuum retard was only for the USA versions of the 34PICT/3 (maybe you didn't read his post carefully enough Colin - he said 31PICT3....not 34PICT3).

The 31 series carbs were used in many countries on the smaller 1300s (for the same years that the 34PICT/3 was used on 1600s - 1971 up). Since the smaller engines weren't seen in the USA once the 1600s came out, the 31s aren't much known there, but there are plenty of them in Australia, South Africa, Europe and so on.

>The '69 does not have a vacuum retard equipped distributor.

Quite right. But it can use any of the 30 or 31 series carbies.

>You will never get a good transition from idle to running in your present configuration.

Nonsense again.

You'll note that the modern replacement Brosol H30/31 has both the 30 and 31 series designations - meaning it replaces all 30 and 31 series carbs.

Both the 30 and 31 series carbs (which have the same throat size) work well with ANY engine from 1200 to 1600, just so long as it's jetted correctly for the airflow. It's at it's limits in a 1600 engine, but that makes for a torquey 1600 which is good in a heavy bodied bus.

For a 1600 with vacuum distributor, the 30 or 31 carb needs a 55 idle, 125 main jet and 125 (maybe 130) air correction jet.

For a 1600 with 009 distributor, it needs a 55 idle, 127.5 (just maybe 130) main jet and a 115 or 120 air correction jet. This makes the engine run a little richer which works well with the 009.

There are tune-up articles for both the "single adjusting screw" and "two adjusting screw" carbies on my web site below.

Rob
Rob and Dave's aircooled VW pages
Repairs and maintenance for the home mechanic
http://www.geocities.com/aussiebug1970/

Sat Jan 04, 2003 3:28 pm

Ok, my bad. I think the carb may be a Brosol replacement. It came in a Brosol box but it says Solex H30/31 PICT on the carb itself. Does the Brosol replacement say Solex on it? I'm kinda new to this game. Anyway, does this mean I may need change the jets as Rob indicated?

Sat Jan 04, 2003 6:45 pm

I think Solex still holds the design rights but Brosol is the manufacturer. What did you end up doing and is it still acting the same?
I have worked on alot of engines with that type carb and have not had to change the jetting on 1600's with 009 or vacume advance dist, some even had mild cams and I have still either been able to tune them or the carb was a dud. ( I am at sea level though...)
The quality control on them is not the greatest, and I have seen some that would not run out of the box and some that went south over a short period of time...
You could try changing the jets but some of those carbs have different style of main jet than the Solex (does not fit size and thread wise) and you may have a hard time finding some to fit.
Hope you get it going or maybe they will exchange it if you take it back.

Wed Jan 08, 2003 6:10 pm

my 74 bug does the same thing but only if its cold outside. It is the same carb witha 009 if its hot out nothing. weird