Dave's '73 Super Beetle has a 1971 1600 dual-port engine. However, a previous owner (or perhaps the mechanic who rebuilt the engine) installed an alternator in place of the generator (used on VW engines up until the mid-1973 model year. The alternator, of course, is "fatter" in diameter at the rear, whereas the generator is the same diameter over its entire length. Dave replaced the alternator, but the diameter of the new alternator was the same as the old one, so he had the same interference with the new setup.
Whether any of this is the cause or not, Dave found that the accelerator pump linkage on the right side of the carburetor was rubbing against and hanging up on the alternator body, causing the throttle to be abnormally open and the idle speed too high. The situation made it impossible to tune the carburetor properly -- a big problem, and an odd one, according to Rob.
Dave found that he had to grind the body of the alternator away a little bit to provide clearance for the accelerator pump linkage so the throttle lever would close all the way and the screw at the top of the lever would rest properly on the stepped throttle cam on the left side of the carburetor.
Dave found that a PO had left the two bottom bolts out where the alternator attaches to the fan housing, probably to shift the alternator over to the right a bit so it would clear the accelerator pump linkage. When removing the fan shroud with the alternator attached, Dave found that he had to take the top off of the carburetor to provide the necessary clearance.
A number of "fixes" were suggested -
Rob commented on this -
This intrigues me - I've never heard of it. Maybe "Speedy" Jim is saying that when VW started using the alternator (in '73) they modified the link on the carburetor. Your's might have had the earlier form of link if that's the case ('71 carburetor). Since you say that this new carby (Bocar) is exactly identical to the old one in every respect (except for the size of the main jet), I don't know what he means by "turning the linkage upside down."
You have three choices:
Dave wrote regarding "bending the linkage" -
It's actually the bolt head on the adjusting bell that impacts the alternator body; I'm not sure how flipping or bending the linkage would change that.
John responded -
Because the bolt is then on the TOP of the alternator, not hanging down. Late model carbs did just this! Just see if you can invert the linkage that actuates the accelerator pump so it's on the top. Then, make sure it works. :-)
Dave was unable to find a spacer to raise the carburetor -- Rocky Mountain Motor Works (now Mid-America Motor Works) had one for '61-'70 (SP) Bugs for $11.95, but their catalog doesn't show one for the DP carby/intake manifold interface. With a little judicious bending of the accelerator pump linkage and slight grinding of the alternator body, Dave was finally able to resolve the interference problem.
Latest from Aircooled.Net on this problem -
Aircooled.Net sells both a Brazilian Bocar 34 PICT/3 ($179.95) and a German 34 PICT/3 ($249.95). The German model clears the alternator; the Brazillian Bocar carb will not. The Brazilian carburetor requires alternator grinding, which Dave learned the hard way.
Disclaimer stuff: Rob and Dave have prepared this information from their own experiences. We have not assumed any specialised mechanical knowledge, but we DO assume that anyone using this information has at least some basic mechanical ability.
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Last revised 4 May 2004.