|
Carburetor Icing
Carburetor Icing
By Jim Thompson
Question from Customer: Hi can anyone help, I've just finished doing the engine on "Boris" my 1200 1973 Beetle, only one minor hitch which is really annoying... runs lovely then stops, checked the engine and the carbs are frozen. If I sit for 10 minutes, then off we go again.... does the air box have a breather hose to allow condensation out?? Why the heck is it freezing up?
Answer: A 1200 73 Beetle sounds like it's from Europe (where only 1200s were sold during the 70s). US Models were usually 1600s. No biggie, because the manifolds and heat risers were similar. What's probably happened is the Heat Riser Tubes coming from the left and right side of the Muffler where they are connected are plugged up with decades of exhaust soot and gunk and not allowing a small portion of hot exhaust air to circulate up against the intake manifold section to prevent what's called "icing". Generally speaking, "icing" usually only happens within the Intake Manifold and inhibits the proper flow of atomized gasoline because it "ices" up before getting to the cylinders. But the heat of the Risers also helps provide a little bit of warmth to the bottom of the carburetor where the throttle linkage and throttle plate are.
To get the Heat Riser to work again requires removing the Carburetor and the Manifold assembly. Once the Manifold assembly is off, take some of the strongest carb cleaner spray you can get and spray it into the heat riser on each end. In addition, get a wire coat hanger to start digging into the crud and remove as much as you can. Once you've gotten deep enough into the riser tube, take a drill and attach the coat hanger to the chuck and start spinning into the riser tube further, alternating between spray more carb cleaner into it to loosen the stuff up It's a time consuming and filthy job (Or drop it in a solvent tank for cleaning parts). Once the riser tube is clean from end to end, re-install the manifold and carburetor and you'll notice a difference in operation and response. The alternative is to get another manifold, new or used (though another used one may still need to be cleaned out). |
|
 |
