Rebuild queries

KKV270 · Post by **KKV270** » Sun Sep 27, 2015 12:59 am

Hi.

Glad to say my 1600cc rebuild is to my expectations.
Question though, the manifold has an inlet/outlet vent just below where the carb sits. I have no idea what this is for. I've been sealing it off for purposes of cranking.

Secondly, the engine idles well but only with the carb choke almost fully closed and goes off on fully opening (I guess I'm back to carb adjustment matters...sad enough, I have a carb with a stuck idle control screw)...any suggestions.[/u]

1300 · Post by **1300** » Sun Sep 27, 2015 1:59 pm

Hello, The outlet on the manifold under the carb is a vacuum port for I believe the auto-stick transmission, in the US anyway. Cap it off well. A vacuum leak will burn a valve. What carb are you using? A 30PICT-1? I would check for vacuum leaks where the head meets manifold. Spray some carb cleaner or starting fluid (ether) at the joints while engine is running, if the RPM's change, you have a vacuum leak. Good Luck, Casey

KKV270 · Post by **KKV270** » Sun Sep 27, 2015 2:55 pm

Thanks for that info. Really grateful.
I am using a 34 pict 3. I earlier had leaks but added gasket papers to seal well.
Cheers.

KKV270 · Post by **KKV270** » Sun Sep 27, 2015 2:56 pm

Question.....for future reference, how does one tell they have a burned valve? What are the tell-tell signs?

1300 · Post by **1300** » Sun Sep 27, 2015 3:39 pm

Hi, if a valve is burned there will be no compression in the cylinder. Poor running. Pull a spark plug wire while it is running using insulated pliers. You will notice the engine running without that cylinder. If there is no difference when wire is pulled, that cylinder may not be firing
Casey.

Sorry, I don't know too much about the 34-PICT-3 Here is a link to Volksbitz website. He has detailed adjustment procedures. If you need it rebuilt or rebushed he is the man to send it to. http://volkzbitz.com/34PICT-3_Adjustments.html

Cribbs74 · Post by **Cribbs74** » Sun Sep 27, 2015 9:36 pm

I'll second the vacuum leak. Make sure your intake is sound and not leaking.

If the large bypass screw must be functional to adjust the carb properly. If yours is stuck then a tear down and rebuild is in order.

Keep in mind you can adjust a carb all day long, but it won't work properly if you have a vacuum leak.

KKV270 · Post by **KKV270** » Thu Oct 01, 2015 2:34 pm

Hi.
Thanks once again for the invaluable info.
Cribbs74, it is the idle screw...not air bypass....either way, what you say about tearing down to rebuild, I believe, still applies.
Thanks for the last note on vaccum leak. I'll go through the whole process patiently yet again just to be extra sure.

1300, for the test on compression against wanting valves, I appreciate as well....
I'll check on my clearances and see if they keep constant or not. I learnt that a constantly changing gap would equally be a sign of wanting valves.
Cheers.

Cribbs74 · Post by **Cribbs74** » Thu Oct 01, 2015 3:01 pm

KKV270 wrote:Hi.
Thanks once again for the invaluable info.
Cribbs74, it is the idle screw...not air bypass....either way, what you say about tearing down to rebuild, I believe, still applies.
Thanks for the last note on vaccum leak. I'll go through the whole process patiently yet again just to be extra sure.

1300, for the test on compression against wanting valves, I appreciate as well....
I'll check on my clearances and see if they keep constant or not. I learnt that a constantly changing gap would equally be a sign of wanting valves.
Cheers.

There are 3 adjustments. Idle bypass (big screw) volume screw, which is the smaller screw below the bypass and the high idle screw for the choke. Which one is stuck?

KKV270 · Post by **KKV270** » Sun Oct 04, 2015 12:23 am

Hi.
The volume screw.

Cribbs74 · Post by **Cribbs74** » Sun Oct 04, 2015 8:05 am

KKV270 wrote:Hi.
The volume screw.

Ah ok thanks, sorry to be so nosey. I assume you already know, but just in case, the volume screw does effect the idle speed, but it is used to control the fuel air mixture at idle. The big bypass screw is what you adjust for the actual idle speed.

Hope you get it sorted out.

Ron

KKV270 · Post by **KKV270** » Sun Oct 04, 2015 3:43 pm

Hey, Cribbs74, please come again.... I didn't quite understand your last post. (please, by all means, make the assumption I know not- I never mind it at all....it is better in any case).

If I get it right, what I might need to be adjusting is the by-pass air passage screw and not volume screw!!!??? (my concern was the engine goes off once I open the choke throttle- I have double checked vaccum leaks...yet to crank again to compare results).

Thanks.

Cribbs74 · Post by **Cribbs74** » Sun Oct 04, 2015 10:56 pm

This link should provide all the answers you need assuming everything is in proper working order.

http://www.vw-resource.com/34pict3.html

That said, the Bypass and the volume control work together to achieve a smooth idle at the correct RPM.

The volume control is adjusted for idle mixture while the Larger bypass screw is adjusted for idle speed.

Hope that helps.

Ron

Blue Baron · Post by **Blue Baron** » Wed Dec 16, 2015 5:54 pm

A 34 PICT carb means you must have a dual-port 1600. You need to post some pictures sometime. I would love to see pictures of you and your car.

At any rate (and since I ignore other people's directions) you adjust the carburetor by first warming up the engine until the choke is off. (butterfly on lowest step of fast idle cam) and then backing out the big screw (air bypass) counterclockwise until you have a nice idle. Then you tighten the mixture screw (small one below the big one) until the engine starts to stall. Then you turn it back out until the idle returns, and then one half extra turn out.

KKV270 · Post by **KKV270** » Mon Dec 28, 2015 3:49 am

Hi Blue Baron.

Talking about posting pics....simple as it might seem, I have always encountered a problem with my pics posting (I even asked for directions once or twice on how to go about it in some past posts). Let me try it yet again.

Please, do give me the procedure you use. Thanks.