Atomic 4 Carb Rebuild
 

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Moyer Marine Parts / Service

?2007 Michael, Matthew and Thomas Arthur

 

 

 

 

Here are a series of pictures illustrating my rebuild of a Universal Atomic 4 Carburetor.  Double click the images for a larger view.

My approach was to install a new rebuild kit and keep the old parts (which were still usable) as spares.  I have had to clean the carb once at a remote location and lived in terror of losing or damaging something vital.  Note:  if you install a new kit, the experts suggest you install all new jets and nozzles (they are sized to work together). 

 

Front Side of carb, after removing from engine.

To remove the carb, disconnet the choke cable....

and the throttle cable.

Note that this carb has the aftermarket PCV valve added. It greatly reduces the hot oil "engine smell."

Begin by removing the flame arrestor...

and the flame arrestor mount.

For a thorough clean, you must clean every passage for gas and air including the scavage tube. Disconnect the scavange tube top....

and bottom.

Remove the main jet plug and the main jet. Don't forget the brown fiber bushing which is often stuck inside the main jet passage.

Remove this hex head plug to more easily clean the idle air passage.

I removed the plug on the bottom of the bowl to clean around its threads.

Remove the idle needle valve completely. When reinstalling, tighten needle against its seat and back it out approximately 1 1/2 turns.

You may need to remove the throttle & choke plates for a good cleaning. The crud on my choke was suspiscoulsly similar to particles found elsewhere.

On this carb which was pretty clean, there were black deposits on the back side of the choke plate.

Open up the carb by removing the screws holding the two halfs together.

Separate the carb top and bottom. (When reassembling, it is easiest to hold the carburetor upside down).

Remove the float by....

removing the pin holding it in place.

Remove and clean the venturi.

Slide the float valve out and remove the float valve seat. Match your screwdriver carefully to the jets or you can easily damage these soft parts.

The float valve needle can be lifted right out. Remove and inspect the float valve seat.

It is sometimes hard to remove the idle jet. If cleaning, leave the idle jet in rather than destroy it trying to save it!

The static air pressure chamber (intake presure). Clean with a blast of carb cleaner and / or compressed air.

Passage to the main jet. Clean it well or she'll run like....

The idle passage. Any tiny bits in here will make the engine idle poorly.

The well vent jet is replaced during a rebuild.

The main discharge nozzle can be removed with easily with an 11/32 deep socket.

Clean all of the passages by squirting carb cleaner or blowing compressed air through them.

Reassemble the carb. After engine is started and warmed, adjust idle mixture screw for smoothest idle. Turn "in" to richen and "out" to lean mixture.

Factory new idle jet magnified 60x.

Old idle jet (magnified 60x). This one doesn't look too bad and will stay in the spares kit.

Inspect the float valve seat carefully. The Moyer carb rebuild kit comes with a pointed dowel to dress it if necessary. Magnified 10x.

Notice the tail on the old style main jet, shown here with the bushing still in place. Don Moyer sells a new main jet without a tail. Magnified 10x.