With Wings As Eagles: Craig P. Steffen's Blog

individual carburetor molecules

2007 June 15 06:39

I discovered a couple of months ago, when trying to make my beetle run right again, that the exhaust valve on the #1 cylinder was stretching. One of the possible causes for this problem is that there is air leaking into the intake side of the engine. More air than than there's supposed to be means a leaner mixture at the cylinders, meaning a hotter running engine. It also means that it's tough to tune the engine properly.

One of the places that air can leak in is around the bushings on the throttle shaft in the carburetor. This is the easiest to deal with because the carburetor is easier to replace, than, say, the intake manifold. I had bought a carb on ebay, so I rebuilt it, and the installed it on the car. Here's the carb taken all apart (click to enlarge):

(The combination wrench in the photo isn't part of the carb, of course. Everything else in the photo is, though, I think)

Here's the empty hull with all the stuff out:

And now ready to go in the car:

And, miracle of miracles, the car runs right! And the throttle doesn't stick!

I think a lot of the issues with the car not running right were probably just passages in the carburetor that were clogged up since historically it hasn't been driven enough. Cleaning the whole chassis out thoroughly with carb cleaner fixed that.

Another thing was the throttle stuck a lot. I had to tap the gas pedal to get the throttle to break loose, so I revved the engine a lot coming off of idle, and so it sounded like I didn't know how to drive a manual. Well, I think this is probably due to someone lubricating the throttle spindle with oil. I've seen this in perfectly legitimate manuals, but do not lubricate the throttle with oil! The oil collects dirt and contaminants, and makes the throttle sticky. Lubricate it with GRAPHITE. It's messy, but it really makes the throttle work like it's supposed to.

So now that I've put in a new carb, and set the timing properly (another story), I've set the valves yet again. The #1 exhaust valve had drifted to .004 inches in 200 or so miles, which is really fast (it should be at .006). So now I have to drive it a few hundred miles to see if the drift has stopped, or slowed down, or is the same as before.