Carburetor vs Dirt Dobber

[GBord]

My Atomic 4 has been running roughly for the 4th time. Before I have rebuilt the carburetor and it fixed the problem. I keep finding junk when I rebuild it so have replaced the filters and lines then the gas tank to no avail.

Today I brought Dave my next door neighbor who has a race car. We took off the carburetor and sure nuff it had junk in the bowl. We sat puzzled as to how the gritty junk had gotten in when Dave pointed to the cabin steps I had removed from over the motor. There were several dirt dobber nest that would resided right over my carburetor intake.

So how do I rectify this problem. If I turn the intake down the the oil exhaust rubber line will not reach it. Anyone solve this one?

Guy

[Marian Claire]

Maybe I am not fully understanding but why not just remove the nest. It will be full of dead spiders and such. I have removed several from my boat. No problem. Dan S/V Marian Claire

[ndutton]

I don't think the dirt daubers are the issue although they should be removed anyway. Assuming the crud you're finding in the carb is in the fuel bowl, the dauber detritus would have to find its way through the flame arrestor (possible), through the intake horn and past the choke butterfly (also possible) and in through the main jet against the flow to get into the bowl (extremely unlikely in my opinion).

If your tank, filters and pump are known to be in good shape (that's a big IF), I'd say it's time to replace the hoses. They are the only other source of crud that comes to mind. They might be old or non-alcohol rated.

[GBord]

It is the crud from the dirt dobers that is causing the problem. "Crud" was sand and the only way to get sand into the carb was from the dobers nest just above the flame arrester. Before I found this to be the problem I had progressively changed the pump, lines, filter and tank on separate occasions. After changing each part of the system and rebuilding the carb the engine would run for several months then begin to sputter and fail (Dirt dobers are a real mince in Dallas).

My thought for a fix is a coffee can with holes on the sides and bottom facing up placed over the air intake. Probably will place some wire screen over the holds to keep the little varmints out of the can.

Would be open to any other solution.

[Loki9]

Can of RAID?

I don't understand the problem, remove the dobbers, problem solved? What am I missing?

[ndutton]

Is the "sand" actually found inside the float bowl? You are reporting sand in the carburetor but where in the carburetor?

I'll also sign on to Dan and Loki's question as to why removing the nest is not an option. That makes three of us so far.

[msauntry]

Its impossible for dirt to fall into your carb and end up in the fuel bowl. You must look to another culprit.

There's no way for sand to sneak through a filter unless the filter is comprimised. Are they intact and sealing as they should? I suspect the problem lies between the carb and the next filter upstream from it.

Check the hoses you used are suitable for the task and not some cheap line shedding debris into your gas.

Check the carb floats and make sure its not corrosion coming off the brass. Was there a layer of varnish that could be flaking off from the floats or the aluminum?

What about your gas tank vent line? Mine was clogged with spiders once, but again, it'd be hard for them to fall into the tank and make it past the filters.

Best of luck!
Micah

[Carl-T705]

Sorry, but I'm not clear on how dirt in the air intake would find it's way into the fuel bowl??? To keep crap from falling into the spark arrester when the engine is not in use ,cover the intake with a piece of metal, plastic, or something to keep stuff from falling in. Hope you can locate the problem. Oh yeah, new doesn't always mean good. I'd recheck the fuel delivery side.

[GBord]

Think of it this way:
Carb air intake is pointed UP. It is only covered by a flame arrister (no filter on Atomic 4) that will let dirt and small particles into the intake. From there the air goes through the small ports that can easily become clogged. It can then find it's way into the rest of the carb (injector tube) when the engine is stopped.

The motor is under stairs so I would like to find a solution that does not require removing them before a trip.

As far as keeping the dirt dobers out! Ha! Reminds me of the the time as a child when I tried to fill a sand mote with water. They are very persistent and evaded most means of riddance. That includes moth balls that smell awful. If anyone has found a sure way of keeping them out please post it.

[Loki9]

I'm not buying it, any foreign material that gets through the flame arrestor is going to be sucked straight into the cylinders. It isn't going to take a detour to the fuel bowl. Still if you are convinced that's what's happening the fix is easy, turn the flame arrestor upside down.

And seriously, try some RAID. The stuff works. You might not be able to keep them out of the boat completely, but you can keep them from coming back to that exact spot.

[ndutton]

Where's the harm in trying?

Rereading the thread I'd say you ought to go with your plan of a tin can shroud and report back with the results. I'm not beyond learning something new.

Please be sure to report back. Now our interest is peaked. And don't forget pictures, we love pictures.

[Dave Neptune]

What Micah said.

There are two basic paths into the float bowl the main way is the fuel supply which goes directly in. The other way(s) are through the air correctors or the three fuel delivery ports int the throat of the carb. Unless the "crud" can swim upstream we can eliminate three of the 5. The air corrector for the main jet will suck in if the "crud" falls back against the airstream traveling into the engine when running~very doubtfull. The last is the idle compensator and it draws from inside the bowl unless the front edges of the two halves are bent and don't seal a common problem on the 4 screw Zenith. It can be fixed by applying a bead of RTV orange over the area once assembled.

So now we are back to fuel. I'm guessing you may have some salt water getting into the fuel. If your tank is truly clean and the lines and filters are fresh all should be well. Are you using a water separator after the tank and a polishing one just in front of the carb? Look for singns of moisture or a bad filter.

Dave Neptune

[GBord]

Dave,
You know this carb better than most so how does grit and grime (fine particles) get into the working of the carb and foul it up if it can't get in through the gas line?

1) I am in fresh lake water (Dallas, Tx) so no salt I hope.
2) I have changed fuel lines, filter(s), tank, pump in that order over three consecutive down times. Each time rebuilding the carb before reinstalling.
3) Installed a small micron filter after the pump this last time.
4) Each time I am finding BROWN GRIT not the black particles you would expect from line or gaskets in pump.
5) Dirt Dobers had a nest just above air intake and there was sand in the flame arister that I noticed this last time now I am looking for it.

I may be wrong on this but the dirt dobers seams the likely candidate.

[Dave Neptune]

Fuel

Gbord, where are you buyng your fuel? Sometimes fuel at marinas is suspect and if you but a a gas station as I do be sure the gas can is clean. I just don't see how the dobber dirt could get inside the bowl. It could get all over the intake throat but not into the pasages necessary to get to the bowl.
Perhaps you are having some E-10 erelated issues.
Try draining from you feed line to the carb a bit of fuel into a clean glass jar and let it evaporate to see if there is indeed anything "IN" the fuel.

Dave Neptune

[msauntry]

Maybe it just needs one more cleaning. Many's the time that I thought I'd cleaned something up and then found more of it later on. There may be nooks and crannies in the carb or lines that you haven't discovered.