Persistant gas drip

[daveinrenton]

Don:

The safety article struck a chord and since you didn't crash in the Arctic, I feel it my duty to not explode on the Puget Sound.

Here's the issue: The little compession fitting on the bottom of the carburator that returns excess fuel to the block persistently dribbles. The tube connecting to the block is solid copper (or some such metal) making it very hard to remove and line back up to get a secure seal. I am convinced the connector is just in crummy shape. What replacement part exists that can replace this antiquated component. I would love something more easily flexed and that gives a very positive seal so I do not have to this case of "post carburator drip".

Dave

[Don Moyer]

Dave,

We list replacement scavenge tubes in our online catalog at moyermarine.com
(product number FCAR_13_60.0).

As a separate but related matter, the fitting on the bottom of the
carburetor intake throat shouldn't really be dripping (the condition of the
fitting notwithstanding). You might remove the flame arrestor housing and
check to see if you have raw fuel puddling in the bottom of the intake
throat. If you do, it would be an indication of a leaky float valve or some
other anomaly in the carburetor. If this is the case, you may also be
seeing more soot on your plugs than normal.

Don

[tenders]

Does that piece have to be rigid tubing? (I guess it's brass.) Rubber tubing is a lot more...well...flexible.

[Don Moyer]

It's very critical that the scavenge tube be 1/8" OD copper tubing so that
the amount of air being scavenged remains at that low level. People have
tried more convenient hoses and tubing with larger IDs and the result has
always been difficulties in getting the engine to idle properly.

Another way of putting it is that any ID larger than that of 1/8" OD copper
tubing (which is almost too small for me to measure) will be seen by the
engine as a vacuum leak.

Don

[daveinrenton]

Don:

When I last serviced the carb, I removed the float valve and cleaned the heck out of all the parts. When I reasembled, it looked perfect as it seated in teh closed position. Is it common as these parts age to have micro-pits or some other such wear that is difficult to see but still allows a little gas to leak through?

Dave

[Don Moyer]

Dave,

We've never seen the pitting you're describing, but we have had to occasionally take a bluntly pointed 3/16" wooden dowel rod and burnish (dress up) the orifice of the seat of the float valve to get the valve to close completely in our shop. Other than those few cases, however, dirt has been the biggest cause of leaky float valves.

Don

[fvigeant]

Hi, I have a simmilar story. Recently dipped my carb and then put her back together. I had an issue with the scavenge tube dripping but that was due to a lack of torque becuase i was afraid of cracking the aluminum carb, after addressing that issues I noticed the dripping from where the choke valve assembly comes through the carb.... looking in the carb further i noticed about 1/4in of gas benieth the flame arrestor. I had recently messed with the fuel mixture screw letting it out a bit and so I screwed that back in a bit and the carb seemed to go back to normal. I noticed a few tablespoons of gas beneith the motor from the dripping so i am concerned if i really fixed the issue. I remember the floats and needle looked in excelent shape when i pulled the carb apart and along with reinstalling it i put in a racor filter and moyer polishing filter. One more thing i noticed is that the fuel mixture screw seems to have little effect on the rpms or sound of the motor is this normal? Do you suggest a total rebuild of the carb?

[Don Moyer]

Your problem is most assuredly caused by a leaky float valve. This is a very serious safety issue for the Atomic 4, and it is discussed on page 1-2 in our service and overhaul manual. I'm attaching a technical discussion of the problem and a few suggestions in the attachment.

Don