Choke adjust for Autolite 4100 Carb





Man, the book has the dumbest darnn procedure I have ever seen. They must have stayed up late to figure it out. OK, you want the silly thing to run properly? Here goes.
First verify that your heat tube, going to the manifold and the manifold passages are clean by blowing through the tube where it would connect to the carb. If you cannot easily blow air through the thing when attached to the manifold, all the carb/choke adjustments in the world will not help.
With that done and all the air passages clear, it is time to do the mysterious adjustment. With the carb cold, loosen the three screws holding the clamp on the black spring housing. Rotate it till the choke plate just closes. Now, mark this point as a reference. Install the carb and start the engine. As soon as the engine hits, vacuum will tend to slightly open the choke. Let it run for a couple minutes. By this time, the black choke spring housing should start to get warm. If you wing the throttle, the choke should 'unload' a bit and be about 1/2 open. If not, and the engine has been running for 2 - 3 minutes, loosen the housing screws and turn it to release the tension on the choke a little. If it is already all the way open, tighten it a little.
Also, set your fast idle screw, with the choke closed, so the engine is running around 1200 - 1500 rpm. The misadjustment of this screw is the most common problem with respect to a cold engine not wanting to stay running for the first couple minutes. Also, make sure your accelerator pump is working properly. An engine will be much harder to start if the accelerator pump is not working and you have to rely solely on the choke to get a rich enough fuel/air mixture to start the engine.