Carb rebuild

[johnr]

I've got a small problem.  In rebuilding my 34pic3, the books say not to touch the small (volume control)
screw, but to remove the large (bypass) screw.  I already took the volume control screw out,  because the rebuild kit had a replacement!  Chilton's on page 46 however, gives adjustment instructions using both screws.  The bypass screw feels like it's welded in,  I'm unable to move it.  (and afraid to try too hard) 

[Bookwus]

Hiya John,

The volume control screw is factory set.  The usual advice is that one should leave it alone.  However, it's really a pretty straightforward affair for resetting it.  When you install your new volume control screw, screw it in gently until it bottoms out.  Then unscrew it 2 1/2 turns.  That gives you a starting point for the volume control screw's final position.  That final position will be determined when you actually adjust the carb for idle.

And the bypass screw.  Are you saying that it won't move at all?  Or that it will move but you cannot get it out?

[hercdriver]

Hi John,

Give this web site a try. I found it spot on.

http://www.vw-resource.com/carb_41.html

This link talks about the "idle control screw".
http://www.vw-resource.com/tune-up.html#idle

from www.vw-resource.com

Also Note: In the exploded view of the carburetor, this screw is called the "Idle Control screw." This is misleading, as this screw is NOT used to set the idle as it was on earlier carburetors. The Volume Control and Bypass screws on the left side of the carburetor are used to set the idle speed.


Turn off the engine momentarily.


Slowly turn in the Volume Control screw until it bottoms lightly. Then back it out 2-1/2 to 3 turns. This is the starting point for this screw.

Note: The Bentley Manual says, "Do not adjust the mixture by turning the Volume Control screw unless (1)you have installed a different carburetor, (2) you have removed, repaired, or rebuilt the carburetor, or (3) the engine is producting excessive emissions." This adjustment is critical - use a flashlight and make sure you have a good line of sight. The Volume Control screw out of whack can cause exasperating performance problems.


Restart the engine and adjust the Bypass Screw until you obtain the desired idle speed (850 - 900 rpm) as indicated on the dwell-tachometer. Turning the bypass screw out increases the rpm; turning it in decreases the rpm.


Turn the Volume Control screw one way or the other to obtain the highest idle speed, then turn the screw clockwise (in) until the engine speed drops by about 25 rpm.

Note: This step is a little tough--it's hard to see a 25 rpm difference on the tachometer, especially if you're using a tachometer designed for an 8-cylinder car. Do the best you can.

Dave

[Bookwus]

Hiya John,

Yep, Rob & Dave's website is definitely the way to go.  They have their act together.

[johnr]

I've printed out those inst. from the website you suggested.  The bypass screw "wiggles" slightly and feels as tho it's welded in rubber.  That's the best I can describe it.  I'll try again to remove it.
Thanks once again to you all.

[johnr]

Problem solved.  I bore down on the little sumbitch and it came right out.  I replaced the o-ring with one included in the rebuild kit and am good to go.  A bit of black carbon-like crud in the passage, shot some cleaner in and blew it out with my air hose.

[hercdriver]

Sehr gut!

Glad to hear it's worked out for you so far. I'll be using the same instructions soon to fire up and tune my engine. I had it rebuilt last year and still haven't got if off blocks. One of these days my honey do list will be finished and the bug will get it's rightful chance at life again.

[Bookwus]

Yeehaw!

Be sure to let us know how it fires up!

Nice going John.